There are lots of different 'pattern' families out there, but taking your question its broadest terms...
I'd recommend:
- Jim Coplien's Organisational Patterns
- The Hillside Group wiki
- Kevlin Henney's site has plenty of excellent links & papers
Offline (my favourites):
- Fowler's Patterns of Enterprise Architecture
- Feather's Working Effectively with Legacy Code
Offline (popular):
- GoF Design Patterns
- Fowler's Refactoring: Improving the Design of Existing Code
