John Berardi is a well known and respected nutrition expert. It’s difficult to browse topics on nutrition on forums without hearing his name mentioned several times. Berardi has written several books on nutrition and has an excellent site at johnberardi.com
One of his books is The Grapplers Guide to Sports Nutrition, cowritten by Michael Fry who is a former wrestler, as well as a grappling instructor for wrestling, jiu-jitsu, and MMA. This books is full of great information that should be known by anybody serious about MMA. Berardi and Fry cover sample menus, supplements, food preparation, training and post workout nutrition, and weight cutting. The part about weight cutting is invaluable, many athletes cut weight dangerously, even dying due to improper methods.
The weight cutting method in this book involves no drastic dehydration, like working out for hours in a sauna (seen many times on The Ultimate Fighter.) This book can show you how to lose 10-15 lbs for a fight without feeling dehydrated and worn out come competition time, and not to mention it is safer and easier than traditional methods.