Any good resource for MOSFET op-amp design?
Analog Integrated Circuit Design
David A. Johns, Ken Martin
Copyright 1997
Chapter 5

To really understand op-amps though, you'll want to understand current-mirrors and single stage amplifiers. The book is fantastic in this regard as it takes you through the basics all the way up.

This separate link has lots of examples of topologies of op-amps:
http://courses.ece.ubc.ca/488/notes/eece488_set7_2up.pdf
Without the background I spoke to before, I doubt you'll understand the reason's behind the topologies shown there tho.