I really like DJ Stawberry. Also Sean Williams is a huge shotblocker. Lasme from UMass is a good rebounder and shotblocker, but not a lockdown defender, at only 6'8". Corey Brewer should be a great defender. Darryl Watkins of Syracuse could be a good lane filler. Those are the guys off the top of my head that stand out as guys that would make the NBA as defenders. Jeff Green is also someone that comes to mind as a guy who will be a good defender in the pros.
Some other guys that I think could/should turn into good defenders based on the flashes they showed as they enter the NBA are Al Thorton, Hasheem Thabeet, Aaron Gray on the defensive boards, Roy Hibbert, DJ White perhaps, Taj Gibson based on that UNC game, and all those long, young, athletic swingmen like Marcus Williams, Nick Young, Tasmin Mitchell, Chris Douglas-Roberts, Mbah a Moute, Thaddeus Young, and Darrel Arthur (at PF).
Oden is a great shot-blocker but he is by no means a great defender yet. His positioning and timing are often awful. I'm sure he will learn quickly in the NBA but he isn't a great defender yet. I think Brewer is the best defensive prospect in this years draft. Collison is great not only at getting steals but as an overall defender. I would say Marcus Dove was NCAA def player of the year last season, but he won't be in the draft. Maryland's Strawberry is also a top class defender.
If you are a team looking D in the future and you cant get the top couple picks. Look to Hasheem Thabeet. He should really stay in college a couple more years to develop but he's not. take a shot if your lookin for a maybe.
His potentiol is Crazy but he's going to need some time to develop. Mid first round.
Anyone on UCLA. I'm not a big fan or anything, but I did see the Kansas game in the regional finals. Probably the most fun game to watch in the semi-boring '07 March Madness. Afflalo is really quick + strong and Collison is super quick and has a nose for the ball.