Cocos2d

Cocos2d is an open source software framework that primarily but not always allows the programmer to use C++. It can be used to build games and regular apps. Cocos2d has a whole suite of tools and variations/branches so it is worth reading the book descriptions thoroughly, to determine exactly what each of them teaches. Arguably this category could also go in the game engines category.

If you know/want to learn C++ want to build cross-platform games, especially for mobile- it is likely that cocos will be a good choice for you.