I personally wouldn't pick a site based on deposit bonus, as (at least in my experience) you have to play about 230980928374928374938 raked hands in order to unlock 1 bonus dollar.
I'd look for a rake back program, or just pick a site that you like the most.
If you win the New Players Invitational tournament you'll get 100% bonus up to $100 and 109 tourney credits, and a subscription to some poker magazine. That's pretty good if you wanna start out small.