you could probably get soriano right now for less than he will be worth by season's end. but texas' bats are heating up so you won't have much longer to do it.
I think Barry Zito is a good buy low candidate right now. I agree with most of the others on hitters. Something else to consider is that most of the Yankee SP's are pretty low right now, if you want to take a risk on one of them you know they'll get wins and run support.