Any advice?

-- Forget the built-in flash; it just won't have the reach (try it if you want).
-- Shoot RAW, so you can easily fix the horrible colour casts from those mercury lights.
-- Use the fastest lens you own, if it's only a short lens, get closer.
-- Maximum ISO on the camera, the DRebel has a pretty quiet sensor.
-- You may find that manual focus works better that auto.
-- Pan with the skaters.
-- Try shooting with -1 stop on the exposure compensation (that will give you a faster shutter speed) and then open up by 1 stop in the RAW converter (that little +/- symbol in the top left of the RAW converter window). This is the digital equivalent of "push processing." Try it with 2 stops (getting a bit noisy).
-- Take your tripod, use the built-in flash in "slow sync" mode for some interesting effects (does the DRebel do 2nd curtain sync??). Slow sync (I think it's call "night" on the DRebel) will also give you reasonable group shots and avoid the black background you will get just using the flash.

Enjoy the party, and take LOTS of pictures (they are free).