Mike Tremoulet (@coffeemike) had an idea to create a cookbook based on contributions from fellow Twitters. As an aspiring chef, he noticed that his friends were talking about upcoming holiday feasts and wanted to see just what they were all going to eat. Based on this he asked his followers to send him recipes. Within ten days Mike had created The Twitter Cookbook (PDF). Another interesting use for Twitter.
You may also want o check out http://twitter.com/cookbook. Recipes given in 140 characters or less that serves three to four people.