There is a need in my workplace to setup a knowledge sharing site, a place where users

• can discuss projects they are working
• share documentation
• ask questions

I am looking for a open-source system that answers these needs, and that can be setup in a week, and requires only PHP and MySQL.

I am a Wordpress fan and developer and could easily implement such a system in Wordpress, however this system needs to be very simple to use for the technically challenged. Without customization, Wordpress users would still need to login to the "back-end" to post. I like the Stackexchange (OSQA) format, but these do not allow for file uploading out of the box.

I do not have experience with Buddy Press, would this be an alternative?