So the NFL is back. It becomes officially official when the players officially reform as a union and officially ratify the deal but all that needs to officially be done by Aug. 4.
Football, for all intents and purposes, is back. Pro Football Talk reports on the timeline of re-opening the league's doors, which looks something like this (unofficially):
On Tuesday, beginning at 9:00 a.m. (Arrowhead time), teams can start signing their own draft picks and undrafted free agents. They can also begin talking to their free agents, other teams' free agents. Team facilities will open on this day as well for voluntary workouts.
On Thursday, teams can begin waiving and cutting players.
On Friday at 5:00 p.m. (Arrowhead time), teams can begin signing other teams' free agents and their own. Full free agency is basically open at this point.
Somewhere in there training camps will start, too.
Keep in mind that the new signings and things like that don't become official until the players ratify the new CBA (before Aug. 4) so, while teams can sign players, they're not getting paid until then.