I believe 220 VAC is considered single-phase power from a lineman's perspective.
tom you are correct, a 240 volt service with 3 wires is single phase in lineman speak. however, each hot wire is considered a seperate phase.
a three phase service would have 3 or 4 wires depending on weather it was delta or wye connected.
here is a partial list of what you can get from the power company:
120v single phase 2 wire
120/240v single phase 3 wire
120/240v 3 phase delta 4 wire
240/480v 3 phase delta 3 wire (no neutral)
480v 3 phase delta 3 wire (no neutral)
120/208v single phase 3 wire (network)
120/208v 3 phase wye 4 wire
277/480v 3 phase wye 4 wire