American Express
General Motors
Proctor & Gamble
Sprint/Nextel
Staples
TD Ameritrade
Of course, let's not forget CBS Radio and all of its various related media outlets.
E-mail them if you'd like, but I usually contact them by phone and follow up with a concise, well-written "snail mail" letter.
The problem with e-mail is that companies get inundated with them. And so few people use snail-mail these days that companies tend to pay closer attention to them (this is also a good hint for sending a resume when you're job-hunting, too).
I'll post phone and mail contact information for all of these companies later this evening, unless someone else posts them first.
http://www.staples.com/sbd/content/help/contact/other_quest.html?storeId=10001&cm_ven=Glamour&cm_ite=emailus