Cinelli Unica, BP Stealth, K2 Razorback, Steel Bianchi roadie, Bianchi Super GL, Specialized Stumpjumper, and 3 beach cruisers
My friend runs this exact setup on his Allez. It's very versatile. He uses a friction shifter for his front mech. If you want indexed though, I think that Shimano just released some Ultegra shifters for flat bars. You wouldn't need to change your rear at all.