According to Pro Football Talk Live (video), the Tampa Bay Buccaneers have $29 million in cap space. (Edit: According to Jason La Canfora, the Bucs have $30 million in cap space). Only the Kansas City Chiefs have more salary cap space right now. The St. Louis Rams have the least amount of salary cap space at $300,000. Division rivals New Orleans and Atlanta have $2.7 million and $1.1 million in cap space respectively, while Carolina has $1.8 million in cap space. When the offseason started, the Panthers were one of the teams with the most cap space in the NFL.
While ESPN reported earlier this month that the Bucs had $15 million in salary cap space, that number was based on the full salary of every player on the 90-man roster. Because the team can only carry 53 people on the regular season roster, ESPN's number is inaccurate. Despite that, the Bucs don't have as much cap space as the $29 million suggests, because that is based on only the top 51 salaries on the roster right now. Once the season starts, all 53 players will count, as well as any players on injured reserve and the practice squad.
Expect the Bucs to extend a few players this season to eat up some of this cap space and ease the cap management in future years. As I wrote earlier, Geno Hayes, Jeremy Zuttah and Sean Jones are prime candidates to get new deals from the team.
Note that salary cap space does not correlate with actual cash spending due to the proration of signing bonuses. In addition, there is no per-team salary floor the team has to meet this season or the next season. An 89% cash floor will be in effect starting 2013, with spending being calculated as an average over the 2013-2016 seasons.