REI stands for
Recreational Equipment Incorporated.
Founded in 1938 by Lloyd Anderson, REI is a cooperative that purchases and produces products with the buying power of its members, then resells it and distributes the profits back to its members.
All of their products are field and lab tested and are 100% satisfaction guaranteed. Their website is located at http://www.rei.com
I know this sounds like blatent advertisment, but I really don't care much about REI. They were just linked as an example on the co-op node and I thought I should fill it. I think I have an REI sweater somewhere and it's decent, but honestly, I'm from Maine and must therefore swear by L.L. Bean. =)