The obvious choice is Joe Flacco. He catches a lot of grief from the media, but some (Jaws most recently) are starting to figure out that he's pretty damn good.

Cary Williams was a major unsung hero last year. He played stout D and even though he doesn't have the natural hands that Webb or Ed Reed have, he made some big plays by deflecting the ball and/or jarring it loose as soon as it got to the receiver. He breaks on the receivers very well. He's also a hell of a tackler for a cornerback.

I think Jameel McClain is pretty underrated as well. He's playing beside the best MLB to ever play the game, so the comparisons are sometimes extremely unfair. He's also a guy who has essentially transitioned between 3 different positions (DE in college, to OLB/DE here, to ILB) until settling in at MLB. He'd be a starter on most defenses. He's young and he's someone who puts in the work to get better.