If you go to your agricultural extension office, they usualy have lots of propaganda on weeds.

Karin, I dont know what State you live in, but there is a book called Weeds of the West, a very informative book, not specific to COmmuntiy Gardens, as I am certain certain weeds grown best in certain areas of the country.
I also know that some plants we refer to as weeds, are weeeds only to us, and not everyone considers them weeds.
Borage and Purslane - considered weeds in most parts of the US, especially to gardeners, are edible as are dandelions, and are considered crops in some parts of the world. As are mints.