I've read about cat nutrition and after I've finished the book I was feeling like switching Nellie's diet completely, but she wasn't fond of a raw diet or something like that, so I tried to find food brands that offer food without too much "strange ingredients"...and you would have found me reading at the pet supply shop for hours...I now often add potatoes, rice, noodles and vegeatbles to Nellie's food and she seems to like it...

I've found a website that may be of interest for you:
http://cats.about.com/gi/dynamic/off...oc.asp%3FID=79