Aderlin Rodriguez is a 3B for the NYM and is a sleeper I like. He is a big kid already with big power and may end up at 1B but could be a prospect along the lines of Wilmer Flores. Ramon Flores an OF for the NYY is also a favorite. He doesn't have the power that Rodriguez has but has a very good bar. Omar Narvaez a catcher for the Rays is one I like also. Nothing outstanding about him, I just have a good feeling. Oswaldo Arcia, an OF for Minnesota is another bat to watch. Rey Nunez, a big 1B for the NYY has huge raw power. He is a little older than the others here but he could be a masher. Exicardo Cayones, an OF for Pittsburgh is another to keep an eye on. More of a speedy CF type. Keep in mind, these guys are in their infancy as prospects and likely wont debut for 4-6 years but could be on a lot more prospect radars in a year or two. They are deep deep sleepers.
Juan Urbina is a guy to watch. Ugueth's son has a lot of potential and could follow a developmental arc similar to Martin Perez. Max Kepler and Jurickson Profar are a couple more guys destined for the top 100 list in the not too distant future. Maybe as soon as 2011.
Here are 2 others who have a shot(2009 reports):
(edit: I posted Martin Perez instead of Carlos Perez...here is Carlos)