This is a list of those declaring for the NFL Draft that should they not declare would still have at least one season of eligibility left. The rule's as they pertain to declaring for the NFL Draft states that a player must be a high school graduate for the duration of three college football seasons. Actual playing experience only matters when it comes to draft value. The complete list can be found here, but in the meantime I have choosen to list the more interesting prospects though truth be told it isn't really to long of a list at this point.
Underclassmen heading to NFL Draft - ESPN
On a personal note it feels kind of good to be gathering information on the draft again.
Declaring
Matthew Stafford - QB - Georgia
Knowshown Moreno - RB - Georgia
Chris Wells - RB - Ohio State
Darrius Heyward-Bey - WR - Maryland
Everette Brown - DE - Florida State
Josh Freeman - QB - Kansas State
Sen'Derrick Marks - DT - Auburn
Hakeem Nicks - WR - UNC
Andre Smith - OT - Alabama
Percy Harvin - RB/WR - Florida (Unofficial but still likely)
Returning
Tim Tebow - QB - Florida
Colt McCoy - QB - Texas
Terrance Cody - DT - Alabama