This is pretty well covered above but make sure you're getting the stainless shanks if you're getting a shank/faucet combo. It's odd how common it is but almost all of the 525SS faucet/shank combos include a chrome shank. (Of course if you decide you can live with chrome shanks you might as well get the chrome faucets too and save yourself a small fortune if you're installing multiple taps).
I ordered my 4" stainless shanks from Ritebrew (bdkelly mentioned them above) because their shank prices are the lowest I've seen and there were a number of other kegging bits I wanted from them as well (their prices are generally quite good). Was very pleased with their customer service and shipping speed.
Got my 525SS faucets from beveragefactory -- a few bucks more than from Adventures in Homebrewing but I was already ordering regulators from them so it made sense. If you're considering beveragefactory give them a call, they're often willing to price match or at least reduce their prices a bit if you can point them to another lower price, though I can tell you from personal experience that they weren't willing to match $29.99 per faucet (which I assume is close to cost if not below) when I asked a month or two ago.