Technically the Huey has always had four 'blades', two of aerofoil section, and two shorter counter-weight balances at right angles to them. This was just Bell's patent system though. As Pyros said the new USMC UH-1Y has the same 'proper' four bladed rotor as the AH-1Z version of the AH1-W SuperCobra.
I've never seen a 3 bladed Huey version though (except in crash photos!)
See:
http://my.core.com/~campholloway/stage1.html
P10 lower right!
Andy "Weeble" Weaver