The NFL's Supplemental Draft is Thursday July 9th. The Supplemental Draft is for the players that were not eligible for the regular NFL Draft. Usually these players have some type of character flaw that has kept them from fulfilling the few requirements that are needed in order to be a regular drafted player.
You might remember the Ravens dipping into the Supplemental Draft a few years ago. Selecting left tackle Jared Gaither in the fifth round of the 2007 Supplemental Draft, Gaither stuck around for 3 seasons only to be a member o the Kansas City Chiefs and San Diego Chargers.