Like Mikey85 said, you can run a fixed gear using a standard hub. I use the rotofix method of tightening down the cog. With the wheel in the frame and chain on the cog, remove the chain from the chainring. Put a rag around the BB shell, then wrap the chain around itl and hold it tight. Turn the wheel backward to tighten the cog. I've never used loktite on the threads but I do use a bottom bracket lockring to help keep things snug. Just don't even think for a second about running brakeless this way, though.

[edit] see link at post #14 for a better description of rotofix.