I would like to build a fixed gear this summer. This is what I'm looking for, one complete bike or frame.
.
1. Raleigh 1970-1979 20.5" or 52cm, Models : International,Professional,Team professional.
2.Trek 1983-1985 50-52cm, Models :760,770,970,170
3.Schwinn Paramount 50-52cm 1960-1980 made with ( 531reynolds ) and nervex lugs.

I've found some old classics like these on www.craigslist.org - go to your local city link and click the "bikes" link in the "for sale" section.

Other sources to keep an eye on include:
http://www.sellwoodcycle.com/consignment.htm
http://www.recycledcycles.net/recy.rtro.html
and
http://www.hampshirebicycleexchange.com/used%20road%20bikes.htm