As Kwise and Texan have stated - HAVE FUN ! Dance ! Don't be afraid nor let your inhibitions get in the way of trying that or approaching that girl who also doesn't have a date either [hey, that situation is improbable, but not impossible].
One lesson that I learned from high school [which will end on friday] is that the experiences are whatever you make of it - so, I'd say don't be too intimidated by the others' discouraging posts...[I'm not intending on flaming you for your views] Let go and don't be afraid of the fun that can happen - just remember that it can happen without alcohol too.
I recommend to go to your after-prom as well if there's one at your school, or just go to the after-prom if you can, if you're more a wallflower type who doesn't enjoy big social events such as dances...
Good luck, and let us know of your experience,
catcha back on the flipside,
will.