I know Blichmann used to sell these. Can anyone tell me where to find 1/2" NPT SS 3-way ball valves? I'd like to use them in lieu of Ts and standard ball valves.
Duda Diesel sells them ... http://www.dudadiesel.com/bv.php
Depends on your setup. If you only want to direct flow from one inlet (say, a pump) to one of two outlets (kettles, chiller, etc), L or T valves will work. If you want to direct from one inlet to two outlets, or pass flow through the valve, you'll want T valves. You may need both depending on your setup.
I'm not sure, as I don't own any 3-way valves, but booking at the diagrams, I'm not sure you can completely shut them off. Especially considering they're full port.
"full port"? I am sure its obvious, but I am missing what that exactly tells me in a ball valve.