I came across this at another board, and thought I'd pass it along to all you good folk.
Also, I've heard that the companies will call you rather than email, so you may want to put your real phone number in. I haven't won anything yet, but I just started last night. If you win anything nice, paypal Veggieboards a few bucks.1- Register a new email address solely for contests. This will keep any possible spam from contaminating your regular email. I like yahoo mail myself.
2- Download a program called Roboform from here. It's an automated form filler, and unlike Gator it doesn't have any spyware or other digital nastiness.
3- Go to Online-sweepstakes.com and have at it! This website maintains a very well organized list of hundreds of contests.