A few of my friends are on Sponsorhouse and got a few sponsors off of they. They dont get free stuff, but they get signifigant discounts on products from their sponsors. They get anywhere from 20%-50% off.
The only bad thing about Sponsorhouse is that to apply to the major sponsors (Thor, Fox, ect) you have to purchase a special membership. I think it goes for something like $200 a year, but if you are serious about it and have a good enough resume to get with some major sponsors, its probably worth it.
I would agree to not acting desperate. Just send them you race results and tell them what you goals are and hope for the best. Attitude means a lot to potential sponsors. They want someone with a positive attiude who will be a good repersentative of their company.