ThinkGeek has all the coolest gadgets, toys, and caffeinated soap for your favorite nerd. They do tend to be a tad pricey, but when you're saving $5 off a $25 purchase or $10 off a $30 purchase, that sweetens the deal.
Coupon code: 9HBB($5 off orders of $25 or more or $10 off orders of $50 or more)
Coupon code: UMASSFLOSS09($10 off $29.99 or more)
What will you geek out on?