The Social Enterprise

I have had a request to approve the use of Microsoft Live Office (their hosted social enterprise solution) which I'd prefer to service using an internal service (it's a bit of a server hugging company here at the moment).

This looks OK for document sharing and discussion, and I've installed it and quite like it :

http://www.o3spaces.com/Page/sp88/ml2/nctrue/index.html

This one looks a bit more full featured, but is still beta and when I tested it that was pretty evident :

http://www.liferay.com/web/guest/products/social_office

I find myself wishing it was out of beta, as it's based on their portal framework, which has a lot of useful portlets already included. Their full portal product is good, but a lot more work than I have time for right now.

Anyone know of any alternatives ? Inexpensive or open source ideally, with MS Office integration.