My advice to you would be to first decide what minimum camera and lens features your going to want to take the photos you'll want to straight away. From there you'll be able to build a system that will evolve
I'd support the CANIKON argument as your more likely to build into a better system. (see http://www.cameralabs.com/forum/viewtopic.php?t=28085&highlight=
Before asking "what brand should I be looking at?" I'd suggest:
What budget DSLR set up for taking indoor snowboarding pictures?
Canon's 50mm f1.8 might be a good option as a starting point lens as its fast, cheap and has a good reputation. Not sure on how good its auto focus is though.
You'll want a decent flash too for indoor snowboarding. Have a look at this post (http://www.cameralabs.com/forum/viewtopic.php?t=28005&highlight=
) for a discussion that's probably pretty relevant
I know this isnt a straight forward answer