3D Text in After Effects - Shatter or Expressions
This video is giving you a few of the options available.
Shatter Effect:
Good - Allows for a quick and easy 3D extrusion, great if you only need some 3D text
Bad - Does not use the camera to create 3D, so if added to an entire scene will look like a flat animation. Like a picture of 3D text.
Expressions
Good - Allows for full 3D and inclusion into a scene, and to be effected by lights.
Bad - Can be a little bit clunky, hard on older systems. If shot from the side can have poor visual effect looking like layers rather than a solid.
It really depends on what you need, but these are 2 options for 3D extrusion in After Effects.