As Dizzyfugu pointed out on the corresponding thread on WIM, the Mil Mi-6 Hook was a winged helicopter that entered widespread service:
I have a feeling that wings are generally more use on big helos than small ones. The conclusion of the Gazelle test team was that the weight penalty of the wings in the hover wasn't worth the benefit in cruising flight. Now obviously that depends on the mass of the helicopter and the typical mission profile. If the wings are a significant fraction of the payload mass and the mission involves multiple take-offs, landings and hovers with short cruise stages in between (as you might expect from a Gazelle) then their conclusion makes sense. On the other hand, if the helo is big enough to have a useful payload in spite of the mass of the wings, and if it typically travels a long distance in between one take-off and one landing, then the benefit of the wings is maximised and their penalty minimised.
Here's another one that flew:
Kaman UH-2A (single-engined) Seasprite fitted with Beech Queen Air wings and a single YJ-85 turbojet on the starboard side in 1964. I presume that the asymetric thrust of the jet unloaded the tail rotor in the same way that the lift of the wings unloaded the main rotor.
From here:
http://www.kaman.com/our-company/history-of-innovationOff topic, but something else I didn't know from that page: Charles Kaman invented the Ovation guitar (the accoustic with a rounded composite back)!
