Those are pretty nice. Looks like you've got your timing and exposure down. The next step is creating stronger compostions. In all of these I think the background is competeing with your main subject.
#2 and #3 are the strongest shots here simply for the fact that you can see the face of the skater. You timing is good and you exposure is on the mark (just like PJ said... I have to read others posts before I type lol) Keep it up and you can only get better.
Shooting with an Olympus Evolt E-510 and loving it