Just finished my Schwinn World Sport thrift shop fixie conversion. Haven't even ridden it yet. Going to take it on a shakedown cruise around the neighborhood, then try 10 mi. or so on a MUP.
Used the original hub with red Loctite, lotsa torque and a BB lockring (sometimes called a "suicide hub" in the fixed gear forum). Got a NOS stem on eBay because the one with the bike was the wrong quill diameter (undersized) and too short a reach. New Vittoria Zaffiro tires from Nashbar. Anything chrome or aluminum got polished with Simichrome. Sold removed components on eBay. Trued the wheels on the bike; they were in pretty good shape. For now I'm just swapping the pedals from my road bike when I want to ride it.
Sheldon Brown's site was invaluable, of course. Got the sprocket and chainring spacers from Harris.
If I take to riding fixed I might strip and repaint the frame next year, and get a "real" fixed gear hub.
Now to see if anything falls off...