We do these periodically on my yahoo group and we've found they're a great way to get in gear writing. We range from someone starting their very first book to multi-published best sellers like Jennifer Cloud and Sherry Derr-Wille participate.
We're starting our newest round on September 13 for two weeks. 1,000 words a day for two weeks. We check in at least 10 out of the 14 days, encourage each other and get in gear. Looking for a writing challenge? come join us:
http://groups.yahoo.com/group/regantaylor/