Allegro?

Is allegro a cool and easy-to-use-while-powerful game library or are there any better ones??

Ryt now I use graphics.h and then i'll move on, but I want to know where to move on!!!

OpenGL:
http://www.opengl.org
http://nehe.gamedev.net
http://www.gametutorials.com

Direct-X:
http://www.microsoft.com/directx
http://nexe.gamedev.net

General:
http://www.gamedev.net
http://www.flipcode.com