R-rated comedies have ruled this summer with "Bridesmaids," "Bad Teacher" and, of course, "The Hangover, Pt. II" performing more strongly than expected.  It's no surprise then that this weekend's new entry to the genre, "Horrible Bosses," is off to a very strong start. 

The ensemble Warner Bros. comedy grossed $9.9 million on Friday for what should be a $24-25 million weekend.  The film benefited from a strong concept (who hasn't had a boss they wanted to knock off?) and starpower in key supporting roles played by Jennifer Aniston, Kevin Spacey, Colin Farrell and Jamie Foxx.  That figure wasn't enough to take the top spot, however as the number one movie in America is still "Transformers: Dark of the Moon."

The Michael Bay threequel found another $15 million on Friday for an impressive $229 million in just 10 days of release.  "Dark of the Moon" will face a huge challenge to its box office fortunes when "Harry Potter and the Deathly Hallows, Pt. 2" debuts on the 15th.  Still, the robot vs. robot actioner should have no problem eventually clearing $300 million domestic.

Debuting in third with $7.4 million was Sony Pictures and MGM's "The Zookeeper."  The Kevin James animal comedy was postponed from its original October 2010 release date after both companies decided it could be more potent in the summer with families after it posted euphoric scores with test audiences.  Unfortunately, something didn't click with the marketing which made the film look incredibly kiddie.  "Zookeeper" should gross $20-22 million this weekend, but it's not the family hit many thought it would be. 

Look for complete weekend estimates tomorrow on HitFix.