Alexi Casilla, MIN and Eric Patterson, CHC are two names to keep in mind right now as both could be in the majors late in 2007 and solid contributors in 2008. Patterson is like his brother Corey in that he is not all that selective but he has some pop for 2B (maybe similar to Brian Roberts with a lower BA).
Casilla is almost a clone of the Twins current 2B, Luis Castillo, though Casilla has better speed and the potential to be a regular 25+ SB guy.
Farther down the list is Eric Young Jr who stole 87 bases in A-ball last season and seems to have a good eye and a bit of pop. This is a big year in his development as he should move to AA and if he has success there, he becomes a much more legitimate option as there is a need at 2B in Colorado.
There is always Dustin Pedroia, but I'm assuming you already know about him as he seems to be the guy the Red Sox are going to give their 2B job to. He just has to do enough to hold on to it, but he is not going to be a big contributor from a fantasy standpoint as he lacks either speed or power.
Of those that may move, Brent Lillibridge is an intriguing guy. The Braves got him from the Pirates in the Adam LaRoche deal and they have an opening at 2B right now. Lillibridge has some developing to do, but it will be interesting to see how quickly that happens this season and where the Braves deploy him (both level and position).
Brignac is a tough call. The thinking is mixed on him as to whether he can play SS on the ML level. There are a lot of scouts who feel he'll be ok and some that think he needs to move. Though the Rays have Zobrist there right now, he is a stopgap, so it seems that Brignac will have a season of AAA to see if he can get the job done. That would seem to say that he won't switch this season anyway.
Two others to watch are Mark Reynolds and Jeff Natale. Reynolds showed pretty nice power across a couple of levels in the D-Backs organization and the key will be whether he can sustain that in 2007. Natale is in the Boston system and, though he was pretty old for A+ last season he did show tremendous plate discipline and some good power. He has a chance to move fast if he can sustain that performance at upper levels and if Pedroia is as vanilla it seems he will be.