Well, paypal does have a list on its site...
Though I am sure you know that and wanted a more concise list since theirs is huge and not terribly well organized.
I noticed that NewEgg started accepting it awhile back which is awesome. Since I am in the same boat you are in sometimes and its very convenient to just pay with paypal. I think Mwave and Tigerdirect accept it too, but I have never used them and have heard mixed things about them.