I'm looking forward to Firefox Book Sprint scheduled for March 17-18. The idea is to create Firefox user's manual from zero in 2 days. Many writers will be collaborating in a wiki environment both remotely (as I will) and on-site (the Sprint is held within DocTrain West 2009 in Palm Springs, CA). To join, you'll need to drop a line to Janet Swisher (jmswisher-at-gmail-dot-com) and register in FLOSS Manuals wiki.
See details here: