Wow! 11 pages on posts to go through! Great ideas from a number of people. So many, that I'll post my comments in 2 separate posts. Here are my favorite ideas among those mentioned already, giving credit where credit is due:
Actress27:
I think they should have a party with the precinct at Castle's place (birthday or release party), Castle and Beckett get drunk, fall asleep on the couch together, Martha and some of the detectives move them into one of the rooms just to lay them down, in the morning they wake up and freak out that they're in a bed together, when they go to work everyone teases them that they slept together (they didn't), makes things awkward, but adds tons of new great lines and humor, then things bland out again, then Alexis gets kidnapped, they have to solve the case together, we get some family moments, Alexis is found and saved, Beckett gets shot in the process, Castle is upset and holding her, he kisses her, they share a moment, she blacks out, wakes up at hospital, he's sleeping there holding her hand she smiles, and BLACKOUT.

rvandsing:
I think the best way for Castle and Beckett to "accidentally on purpose" kiss is to have a holiday episode with mistletoe and have both of them accidentally meet underneath it with the rest of the cast nearby to observe. You could have the entire episode use the mistletoe as a running joke with each of them narrowly avoiding meeting underneath throughout the episode as a case is solved and then at the end get accidentally stuck underneath and be forced to deal with it. The reactions from the rest of the cast could be "embarrassing" or funny or whatever to spark the denials that would undoubtedly come from Beckett about her own feelings from the kiss.

itsmyworld:
I admit, I'd love to see some undercover work with the two of them having to play a married couple or something. Like at couple's therapy to get information on the therapist. That could be hilarious. They did this in another cop show, the Unusuals (did anyone watch that?) and it cracked me up. It could be especially fun with these two.

Cask-ett:
Or maybe even Castle and Beckett get excited over something happens to them and it's just a spur of the moment out-of-no-where kiss.And then they stop and look at each other and can't believe what just happened.

kemppro:
Castle gets shot by a "perp". It's not life threatening but it does put him in the hospital. It has to be Castle because you know he'll wear his scar like a badge of honor AND argue with Capt. Montgomery when he tries to curtail Castle's shadowing because it's too dangerous.
He's recovering in the hospital when Beckett comes to see how he's doing. He's asleep and she sits there watching him with concern and consternation because she's the reason he took the bullet – yeah, he took it in the upper scapular area when he was throwing her to the ground.
After the musical "flashback" of their times together which ends with Castle telling her she's extraordinary, she gets up and, with tears in her eyes, tenderly kisses him while he sleeps.
As she exits the room Castle opens his eyes and smiles…

This last one from kemppro is my favorite!

OK, now for my own person ideas on how they'll get together. I posted some fanfic entitled "The First Kiss" on the "Get Creative" forum, so that's one idea I had (sorry for the shameless self-promoting plug).

I don't know that the two of them going undercover would work, since Castle is so well-known and people everywhere recognize him. I have thought of them both going "undercover" in a nightclub, Castle being himself and Beckett being the entertainment (this way we get to hear Stana sing!). I can see Castle hanging out at the bar, flirting with women like he always does, and he hears the most incredible singing voice come from the stage area (like Flynn in the The Librarian 3). He turns away from signing some woman's breast and see Beckett in another of her incredible dresses putting on the most sultry, amazing performance he's ever seen. His jaw drops and from that moment on until the night is over and the case is solved, he's mad for her. She comes over to his place after the case is solved for some innocent reason and Martha and Alexis are out. They talk about the case and he finally tells her he's fallen for her. Beckett, for her part admits she couldn't stand seeing him flirt with other women and after a pause, they kiss passionately.

I'd love to see something similar to what others had posted about Alexis or Martha being kidnapped. Maybe the person who order Beckett's mom's murder gets tired of Castle & Beckett nosing around on the case and kidnaps Alexis or Martha … or even Beckett's Dad. In the process of trying to rescue the kidnapped person, one of them gets shot and ends up in the hospital seriously injured. I liked kemppro's version of when Castle gets shot so much, that I won't try to improve on it, but how about this for if Beckett is shot. Castle comes in to her hospital room and sits on the edge of the bed, looking at her, hating himself for allowing her to get hurt. He takes her hand in both of his and tells her that he's grown to care for her deeply, that he can't bear to not have her in his life, and that he loves her. He kisses her hand, then leans forward and kisses her gently on the mouth. He tells her to get well because he misses her, then stands up to leave. As he turns, he sees Captain Montgomery, Lanie, Esposito, Ryan, Martha, Alexis, and Beckett's Dad all standing peering in a window into the room. He is embarrassed to realize that All of them saw what he did and all of them know his true feelings.

Another thought I had for the unplanned hug or kiss that is brought on by a moment of tremendous happiness, could be when one of them (could be either one, but I think it'd work better if Castle was the one who was shot) returns from having been in the hospital after being shot. Beckett could be called into the station on some pretense by Capt. Montgomery, and somehow convinced to get a cup of espresso in the break room or to go interrogate a suspect waiting in the interrogation room. Beckett enters and finds Castle sitting there all bandaged up waiting for her, one of those wry grins on his face. In front of the whole precinct who were all in on the surprise, Beckett forgets herself, walks right up to him, and hugs him, leading to a short but passionate kiss. Everyone in the station, especially Lanie, Esposito, Ryan and Montgomery, all applaud.

That's all I got right now. Sorry to have gone on for so long. I just love thinking of scenarios that finally put them "together".

abc123, his agent told him about the chance to write some "British Secret Agent", and the music in the background was clear enough to recognize James Bond theme… :)

Oh, I like the elevator idea, Pam. by the way where did you get the photos in your avatar?

pamfromcalif said:

To abc123 Either a black out in the city or a snow storm that keeps them from getting anywhere so they have to be together alone without interruptions from family or the police dept.
Also think the elevator could be fun, stuck in there for a few hours and they end up kissing, after they get out they act as if it didn't happen and then keep watching the other for signs that it meant something to them.

The elevator idea is really great one :)

Nev827 said:

Thanks Pam. I've found a lot on forgottensecrets.com, and IMDB, but not the other sites. Thanks a lot. This just adds more fuel to my obsession!

This one is also worth visiting :) – http://www.swannees-place.com/…..ason2.html

I've been up late tonight reading the 11 pages of posts on this — no way I can get caught up.  Haven't been back to this forum for awhile (my mom passed away and my husband had open-heart surgery — sorry for throwing that in, but it's only now that I've felt like getting back into the Castle world again).  Have never missed an episode of the show though.  Loved the one where they were jealous of each other's date.  Couple of comments about the first kiss.  Doz — you took the words out of my mouth about "Scarecrow & Mrs. King."  It was one of my favorite shows, because they just kept getting closer all the time.  They did a couple of undercover shows, I believe – one on the cruise, one where they moved into a neighborhood and posed as a married couple…and now that I think of it, another one where they went on a retreat somewhere.

I'd thought of the undercover plot, too.  Seemed like a great way to "force" them to get closer for the sake of the job.  BUT:  as Nev827 pointed out, I veered away from that because Castle is too well-known.  He was just named one of the most eligible bachelors – in the newspaper, etc. – how can he go undercover??  Unless maybe there's a disguise involved?  That could be good.

I really think the writers are moving them forward just about right, even though I want to scream sometimes because they come so close, yet not close enough for my romantic mind!  But they sort of had a "date", with the hamburgers…they're jealous of each other's dates…it was mentioned in the bachelor episode that Castle had spent his time talking about Beckett.  Maybe we'll get a spontaneous hug or kiss soon, even without a major plot moment.

I agree – you don't kiss someone "accidentally" – but you do kiss them spontaneously, without any planning. 

Anyway – no new ideas to add, just comments –

Hey davidsmom: so sorry to hear about the death in your family. I had a very sudden death in the family a couple years ago and still have a tough time dealing with it periodically. I'll keep you and your family in my thoughts.

OK, back to topic. I agree with you about the writers striking the right pace with the Castle-Beckett relationship. They're doing a great job with not moving too fast, though I'm sure some would argue they're going too slow! they're really doing a great job of building a solid friendship on which a great romance can be based.

Davidsmom, I am so sorry for your loss. I hope your husband makes a full recovery. Wishing you the very best.