At any other time of the year, a $14 million take would probably get you a decent ranking in the Top Ten. This holiday weekend, that box office total was enough to put Tropic Thunder into first place. Again.

Despite a new Vin Diesel entry, the Ben Stiller comedy led the top of the pack for the third weekend in a row. (If it reaches that mark a fourth time, it will have officially reached Dark Knight territory.) Meanwhile, Babylon A.D. settled for second place with only $11.5 million in ticket sales. I’m guessing the sci fi film’s reviews - in particular, the one from the movie’s own director - might have had something to do with the disappointing turnout.

In other box office news, The Dark Knight‘s $11.1 million weekend officially pushed the sequel past the $500 million mark. The only other film to accomplish that achievement is 1997’s Titanic ($601 million). Mammia Mia! also found something to celebrate this Labor Day. Thanks to a special sing-along version, the musical actually had a better performance than it did last week.

1. Tropic Thunder, Dreamworks/Paramount, $14,602,121 (avg. $4204)
2. Babylon A.D., 20th Century Fox, $11,541,571 (avg. $3405)
3. The Dark Knight, Warner Bros., $11,127,290 (avg. $4046)
4. The House Bunny, Sony, $10,177,701 (avg. $3750)
5. Traitor, Overture Films, $10,006,327 (avg. $4872)
6. Death Race, Universal, $7,889,755 (avg. $3110)
7. Disaster Movie, Lionsgate, $6,945,535 (avg. $2629)
8. Mamma Mia!, Universal, $5,421,815 (avg. $2755)
9. Pineapple Express, Sony, $4,448,782 (avg. $2173)
10. Star Wars: The Clone Wars, Warner Bros., $3,764,410 (avg. $1540)

(You can review last week’s numbers here.)