(sometimes it's helpful to include what search terms would work...)

IRO gets great reviews all the time and is a wonderful option for lots of reasons. other companies selling affordable SS/fixed gear bikes are bianchi, KHS, Fuji, Raleigh, specialized. or, mercier and its "bikesdirect" brethren, motobecane messenger, dawes lightening (low-end stuff branded with older, respected names that BikesDirect bought the rights to)--always available on ebay.

www.sheldonbrown.com has an article about converting old road bikes to fixed gear or single speed. also on what to look for from an old road frame. these can be found at thrift stores, garage sales, garbage piles... once you start looking for parts to scavenge, you'll start seeing scavenge-able parts all over the place.