Not sure what to recommend for you...if you can't be on the rink then it's not always easy to get close shots without longer focal length, which limits f-stops. You could possibly use flash to get a 1/250th sec speed (20D's max x-sync), though your distance may be too great; I'm not sure. Or, if you can get in closer somehow, you might consider an EF 85mm f/1.2 L in the future.
Last February, I took this one with my Rebel XT and EF 50mm f/1.8 II @ 1/160th, f/2.5, ISO1600, no flash. It's not a speed skating shot, but it IS a skating shot, of a very, very skilled dance skater, as he's rotating. I was on the rink with him, so distance wasn't a problem. I underexposed a little to get a faster shutter. This was shot in JPG; it lightened up fairly well, though I couldn't safely push it past the level shown.
On a side note, I was ordered to put my camera away that night because some people complained to the manager about me taking pictures during the session. Interestingly enough, noone ever complains when someone's carrying around a little compact and snapping shots (WITH FLASH, I might add). And I've seen people on the sides with their Sony prosumer cams flashing away, and they never get told to cease and desist. I didn't know I was that scary ;\