Review of Box2D powered by the Slant community.
A 2D Physics Engine for Games
Ranked in these QuestionsQuestion Ranking
Pro Permissive ZLIB license
Pro Has wrappers for various languages
Besides C++, there are wrappers for C# (Farseer physics), Java, Python, Action Script and many other languages.
Pro Cross Platform
Works on pretty much all notable platforms (Windows, Linux, iOS, Mac, Android)