With my job, I end up using RadioShack a lot to pick up wires, switches, resistors, etc. RadioShack always has what I need. I prefer to pick up things online if I have to, because of the prices, but if something breaks down and I don't have a part, RadioShack will almost always carry it. Even rare parts are commonly stocked by RadioShack, which is a big plus for me, because sometimes, what I am working on is extremely time critical.
RadioShack gets an A+ in my book.