One song always gets me in the groove:
Hot Hot Hot – Buster Poindexter
I’m sure there are others, and I’m sure I’ll think of them, but go ahead and add some of yours…
Currently, pretty much anything by the Egyptian duo Aly & Fila. They do a variety of collaborative dance mixes with lots of artists. Their big tracks right now are Whatever and How Long (which isn’t on their website playlist yet). You can see several videos of them here, here and here. They absolutely know how to build up a tune and set a dance floor on fire. I’d love to see them come to America, but they haven’t paid us a visit yet. They’re really making a name for themselves in the international dance scene thoughout Europe, where all the best music comes from (notice the videos are from a club in London), so I’m hoping they’ll make it over here eventually one day soon.
There’s also the New York duo Filo & Peri. They’ve put out some killer tunes as well. Their big track right now is The Anthem, but Ordinary Moment remains my favorite of theirs. Give it a listen, it’s the first one that comes up on their website playlist. It’s an instant classic to me, truly an amazing blend of genres in the realm of dance music. The refrain has a softness that juxtaposes with the driving nature of the rest of the song, breaking up the beginning and ending passages with a moment of deep tenderness and beautiful longing, and some amazing lyrics to boot, too:
All I want, is an ordinary moment here with you. No distractions.
Tell the world that you’re busy doing nothing, cancel everything. Let it go.
Meet me in the kitchen, at the table. I just want to be alone with you.
Stare into the eyes I’ve been missing, don’t say anything. You don’t need to.
We’ve been working so much, we’re forgetting to touch. What have we become?
Did you know that it’s a crime, to never find the time … to love?
Both of these groups give me goosebumps and make me feel like flying whenever I hear their stuff. Sorry if the genre isn’t what you had in mind, but I’m living in 2007, rather than 1987, and this is where the real dance music is at today. 
Yes, it’s true Buster Poindexter was hot hot hot 20 years ago. How old ARE you? I kid, of course, it’ll always be a fun song. 
Stevie Wonder has a lot of good ones, particularly My Eyes Don’t Cry No More.
Now do mean legitimate dancing, or just wildly thrashing around to loud music? If you mean the second, there’s tons of punk records I do that to when I’m by myself. 
For the former, “Daft Punk Is Playing In My House” by LCD Soundsystem always does the trick.
I don’t really dance, but anything that’s really funky. Not Disco, but Funk. JB, Sly and Co., George Clinton/Bootsey and all thier apparitions, some EW&F, some Ohio Players, Wild Cherry playin’ that funky music, some KC and the Sunshine Band (I know they’re pretty much Disco, but they were pretty funky in their own right… I dig horns!), Average White Band big time, some RHCP with Dave Navarro, For the Love of Money (forget who did that), that Chef is a baaad mother…, Curtis Mayfield, many others.
Don Henley — “All She Wants to Do is Dance”
Sly and the Family Stone’s “Dance to the Music.”
Has anyone else ever heard of that? lol
Led Zeppelin riffs sends electricity through my legs and usually I can’t stand still. I need to dance like Atomic Elvis. Songs? Like “Whole Lotta Love”, “Heartbreaker”, “Black Dog”, “Rock and Roll”.
Joe Haymes’ Limehouse Blues (1933).
Warning! Nervous-White-Guy music. Channel spirit of Steve Buscemi before playing.
Groove Is In The Heart by Dee-Lite and *It Takes Two * by MC Rob Bass and DJ Easy Rock are two songs that are guaranteed to get me onto the dance floor at weddings and whatnot. I’m sure there are more contemporary dance songs I’d love, but I don’t listen to the radio and I don’t go to clubs.
I know they’re from the same era as Hot Hot Hot, but after being on a couple Caribbean cruises and hearing that song played endlessly on each one, if I ever hear it again I have to stop myself from jamming chopsticks through my eardrums.
Neil Diamond’s “Brother Love’s Traveling Salvation Show”
I’ll see your Stevie Wonder (which actually moved my brother, a grown man, to dance in his underwear in the hallway of a Vegas hotel) and raise you one “Smooth” by Santana.
Always move to “Burning Down the House” by Talking Heads.
Seem to be short on articles and pronouns today.
“Carmen”! … um, does marching count?
We also used to get up and dance when The Jefferson’s came on. “Well we’re movin on up, to the East Side!”
“Rosalita,” by Springsteen.
“Canned Heat” by Jamiroquai… it’s a song about dancing and I can’t listen to it without groovin’ out.
I submit that it is impossible to hear Whole Lotta Shakin’ Goin’ On by Jerry Lee Lewis without at least bouncing around in your seat.
“Come On Eileen”, by Dexie’s Midnight Runners
Funnily enough, the music that makes me want to dance the most is some of my least favorite music to listen to. Current fluffy pop (Fergie, Akon, Gwen, whatever) and goth-tinged industrial or techno always get my ass moving.