Here's just a few I've found, feel free to add your own!
First I have to start with some shameless self promotion, lol. Shopping in the following two stores helps support The Warpath, check them out!
The Warpath Redskins Fan Shop: Jerseys, hats, mugs, and more!
CafePress Warpath Shop: Official site merchandise
HATS:
Redskins hats at hatland.com