Look here for hundreds of conversions.
http://fixedgeargallery.com/
Lugged bicycle info. here.
http://www.terrafermacycles.com/joinery/lugs/lugs.htm
The Sheldon Brown link provided by Jive Turkey will get you started. After you read that, come back and use the Search function before asking questions as it will save you a lot of abuse.
Good luck!