Looks like a great thread developing here....
I got a 30d last year, used the excuse of new kid...new camera
Since then bits n pieces (camera) have increased.... and the type of photos im taking - not kiddie.....
Have a look at the pictures here....
http://www.flickr.com/photos/26932665@N03/
Im not racing anymore, but i get to take picturesd for the web site I run
http://www.msabritishautocrosschampionship.co.uk
I can recommend some info:
Ive hired a lens for the last 2 races i have done, 70-200 IS Lseries F2.8 it is some kit, though Its really expensive!
Try getting second hand stuff (ebay is ok) though you may not get a warranty, though places like jacobs, London camera exchange and Apature Uk offer 6 month wty on 2nd hand kit. Canon is really good for kit turn over so you can get it at reduced prices, Id go for canon kit rather than Tamron unless your buying really high end kit.
I dont know what price range you have in mind but I can recommend a good value canon lens 50mm F1.8 its about £90 (Warehouse express) you'll get some craking shots with it as it is a Prime lens (ie fixed focal length).
WRT shutter life I use my camera nearly every other week and I have not had any problem, however my collegue at work has a Nikon D60 low used and every now and again the shutter sticks!
I got a 28-135 is lens its pretty good all round though you'll need to pick a lens for the type of pics you want to take!
PM me if you need any specific q's answering..
Cheers
Michael
P.s. paid £25 for my tripod its light and holds the weight of my camera (and a 90-330ES), though wouldnt like an Lseries lens.....