DMN Blog reports the following key off season dates relating to free agency and the draft.

February 7-21: Period to tag franchise and transition players
February 20-26: NFL combine
February 28: Deadline for qualifying offers to restricted free agents
February 28: Free agency starts at 11 p.m. CT
March 30-April 3: NFL Annual Meeting, Palm Beach, Fla.
April 18: Deadline for restricted free agents to sign offer sheets
April 26-27: NFL Draft (Update: sorry for forgetting the big one)
May 19-21: NFL Spring Meeting, Buckhead, Ga.
July 15: Deadline for franchise players to sign offer sheets