The server software powering http://www.EditThisPage.com/ and now also http://www.ManilaSites.com./ (at both, anyone can start a ManiLa site which can be open to others) among other interactive projects. Manila itself is of course at http://www.manila.com/

See Wiki:ManilaByDaveWiner for previous discussions about this software. The Scripting News site at http://www.scripting.com/ may also be of interest.