So did I see you said you want to race electric cars...?
You could start with a relatively low-cost (say a couple grand, depending on how fancy you get)
Electrathon race car. We used to build them back in the day before we became team 1346. I've put some video up on youtube here:
http://www.youtube.com/watch?v=yjO6xp-Tz8Y
Or you could go "big time" and do electric drag racing:
http://www.nedra.com/
There are many, many articles available on the web concerning electric vehicles and mods, etc. While lithium batteries are cool, most conversions still seem to be based upon lead-acid, simply due to the fact that you can get huge amounts of current for relatively low cost.
If you want to work with lithium batteries without breaking the bank, may I suggest using them for radio-controlled electric airplanes? For a few hundred bucks you can build a plane with a thrust to weight ratio greater than the F-22. We are building them in my Engineering 12 class and tried replacing the NiMH batteries with Li-Poly today. We can now launch the airplanes straight up... no taxi... no runway... just straight up like a rocket. Now THAT is cool.
Jason