Birdman has decent prices. Also check out Adventures in Homebrewing and Farm House Brewing Supply. Don't forget to factor in shipping when you shop because that will often be the difference in terms of price...
Check out Keg Connection too. One thing to keep in mind, some shanks have welded on tail peices. I personally like the ones from Keg Connection because I can take the tail piece off when I really want to clean everything good (i.e. after having a sour on tap). Not sure functionality wise it really makes a difference, but makes me feel better about it.