More information on fruit picking?

I've been slowly planning my first backpacking trip for about 2 years now (I know, I'm slow at this!) and my only problem was with one question: "how am I going to pay for this!?" And then, as if the heavens opened up and an answering light poured out over me, I came across a post on this website about picking fruit. It's perfect for what I'd love to do! I would like to alternate with work and travel with the on and off seasons of the fruits. I've had some fruit picking experience on my family's ranch in Oklahoma, so I have a general idea of how hot it can get and tiresome.

Now to my request, any info that you think might be useful is great!
First of all, does anyone know of a website that can hook me up with jobs in the U.S. picking fruit or vegetables that have similar systems to the Austrailian ones? I love the way the system looks there where you come and pick during the season, and nothing ties you down to the place any longer. And the benefit of not having to apply for visas every time I need a job would be great.
If not, does anyone know if there is a limit to how many Austrailian or Canadian working holiday visas one can aquire in his lifetime?

Thanks a ton!