I don't know much about the AL so I won't even venture a guess, but in the NL....
The Giants in the West (They're just too good, even without Bonds)
The Braves in the East (The Phillies might give'em a run for their money, but they're in the middle of a 27 day road trip and that's got to be tough
)
The Cards in the Central (With additions of DeJean, Hitchcock and Matty Mo coming off the DL and J.D. Drew and Vina coming back soon, as long as they stay healthy, they're good to go)
It's a toss up for the Wild Card, but I'd go with the Cubbies. Normally, I'd say wait till September and watch them crumble, but this year they've acquired some intangible spark.....)