I have been buying Frontier Charcoal from Sam's Club for 14 dollars for a 40 pound bag. My first bag I got 32 Hours worth of smoking time out of it and was impressed. The only problem is I recommend you feel the bag when you buy it because the first bag I had was allot of small pieces while the second is full of the good lumps. Here is the review.
http://www.nakedwhiz.com/lumpdatabase/lumpbag95.htm
http://www.nakedwhiz.com/lumpdatabase/lumpbag95.htm