Eric M. Burke: "What I have not seen, however, is a good system for preventing stale documentation. The concept is pretty simple. Provide an RSS feed for the least recently modified pages on your web site. Or maybe configure several parameters such as how many page views pages get, how many people link to those pages, etc.
Every week or so you could review the list of "stale" pages and make educated decisions. If the pages are still valid, just click a checkbox saying "reviewed, OK". Or, update the page or even delete it."