We use CentralDesktop, we post a number of GoogleChat and SkypeChat transcripts there as well. CentralDesktop has a search engine that can search each workspace

We use CentralDesktop, we post a number of GoogleChat and SkypeChat transcripts there as well. CentralDesktop has a search engine that can search each workspace, attachments, EditGrid is embedded for spreadsheets, and a good contention management system (when you are working against a deadline you will run into more than one person trying to edit the same page, most wikis don't manage this very well). We create separate wikis that we use to work with customers and partners so that knowledge can be compartmentalized and security maintained.