After the last two positions where pickings were slim, we get some good choices here--and that's despite the fact that we just miss out on a bunch of very nice players. Here are the young players and prospects that are just out of reach: Ryan Zimmerman, Nationals; Alex Gordon, Royals; Brandon Wood, Angels; Chase Headley, Padres; Andy LaRoche, Dodgers; Ryan Braun, Brewers.
That said, the position is still deep in prospects. There are two ML-ready players under 23, and two very, very strong prospects that are extremely young still.
1. Evan Longoria, Rays, 10/7/85, 22
He's the #1 prospect in the #1 farm system. Do I really need to say more? Longoria looks to be a .300/30/100 player when he matures. Note: that would put him in hall of fame territory, if he stays healthy. He's really that good. He's not fast, but he has great footwork, hands and good arm strength, and therefore should be above average defensively.
Basically, if you were going to start your team around a young third baseman, I'd pick him before any of the guys above--including Ryan Braun (who's no longer a 3b, anyway).
2. Ian Stewart, Rockies, 4/5/85
Stewart's become the forgotten man, he's been the top 3b prospect for so long. Unfortunately, he struggled a bit in AA, but seemed to recover nicely in AAA last year. He's ready for the majors, but with Garrett Atkins ahead of him, one of them will have to be traded, or Stewart's going to have to settle in at second.
3. Josh Vitters, Cubs, 8/27/89, 18
Vitters basically looks a lot like Longoria, although much farther from the majors and much less of a sure thing. Still, he looks to be very good for a very long time.
4. Angel Villalona, Giants, 8/13/90, 17
Sorry Giants fans, he won't help out for a while. That said, he was impressive as a 16yo in rookie league. He may end up as a first baseman, though, as he fills out. He hit .285 w/ a .450 slugging percentage. Did I mention he was 16? And by the way, he was 16.