Liferay: open source CMS/portal: looks good
I saw a reference to Liferay this morning and took 15 minutes to install it and start to experiment with it.
After even a short look, I must say that it is impressive: a document repository that allows searching a variety of document types, many plugin portlets (blogs, message board, SMS messaging, wikis, etc.) that each user can plugin to their home page.
I have been largely ignoring the Java portlet specifications, etc. Time to dive in...