After doing a lot of research and attempted to use many wiki systems, we've settled to using Wordpress as our help system. It's got decent search, hierarchical

After doing a lot of research and attempted to use many wiki systems, we've settled to using Wordpress as our help system. It's got decent search, hierarchical articles that you can easily map into categories, many plugins and so on. To accomplish this, we've created a custom theme/layout that renders the help categories in a JQuery tree plugin on a left sidebar , search on top and content on the right column. The effort was about 2-3 days for one frontend developer and the results were quite good, so I highly suggest going this route unless you have other restrictions.