I used an 85 or 100 watt "PAR38" (landscape type) flood lamp (red) bulb. I bought it at Home Depot and it worked really well. I hung it from a string so that I could raise it or lower it to get the right temp in the brooder.
Check out these directions for a homemade brooder: http://www.poultryhelp.com/brooders.html
Check out these directions for a homemade brooder: http://www.poultryhelp.com/brooders.html