Just about everyone uses www.rockymountainatv.com I also like www.nossmachine.com http://www.magicracing.com/ http://www.jlatvproducts.com/. If you want to see microphisch (sp) for oem stuff go to www.ronnies.com
Depending on the product, you have Dave who owns Noss Machine and builds trick heads and other parts, Boonman who lightens flywheels and shaved heads, you have Jim at Passion Racing who builds a lot of the guys motors here, CottenEyeJoe who fabs up all kinds of stuff, Holyman can get you some bearings and I believe Amsoil, DuneDemon can get shock springs, and the list goes on and on. I know I'm forgetting something.
Oh, and welcome.... it's all about fun!!!