I use [JSPWiki] with [Resin].  I work for [Caucho|http://www.caucho.com] so I may show a [Resin] bias ;-).

I have a couple of things I use it for:

* building some free form website's for use by people who may not be very technically literate

* an attempt to organize the massive amounts of junk, ideas, correspondence in fax, email, and snail mail form, etc. that acummulate so rapidly on my computer