Telligent Community combines blogs, wikis, forums, and file-sharing capabilities into a single product with single sign-on, using all Microsoft technologies. Is there an equivalent offering that runs on Unix/Linux? Or would I have to pick and choose individual product offerings and figure out another option for single sign-on across them? Are there plug-ins for something like WordPress or MovableType that might add the necessary functionality?
A friend of mine is looking to add a "members-only" area to her company's website, and since they're hosted on Dreamhost (and can't afford StackExchange pricing yet), I'm trying to find other options for them.