There are several good books (some already mentioned) on design patterns. I actually have around four or so. When learning a pattern I like to read about it in more than one book. Usually the scenarios and examples will be a little different, which helps get the idea better. Wikipedia.org is a pretty good resource too.
That said, I like to spend some time reading code related to the patterns. Code that shows strengths of a platform is nice for obvious reasons. Check out http://www.dofactory.com while you are at it. If you want to see the GoF and other enterprise patterns applied to some real coding problems, then that site is excellent. You have to pay for the reference app and design patterns solutions, but there are examples related to the Head First book, the GoF work, and what they call optimized variations that leverage .NET.
Some books I found useful:
- Head First Design Patterns: Great book for getting the ideas.
- C# 3.0 Design Patterns (Judith Bishop) : Not my favorite for the code examples, but there are usually some nice points around comparing a pattern to other related patterns and why you might pick one over another.
- Design Patterns (Christopher G. Lasater): A pretty good book that is straight to the point.
