Read the Docs Hackathon
If it's around regular business hours, you have to check in with the front counter on your way up.
Unfortunately the building will be locked, so you'll need to text 503-208-6512 or ping Wraithan in the #readthedocs channel on irc.freenode.net when you arrive and someone will come down and let you in.
We will gather and hack on Read the Docs all day. If you've never contributed before, this is a good chance since both of the main maintainers (one of which is the original author) will be there.
There will be pizza, snacks, drinks and beer provided by Mozilla to fuel folks.
If you want to get started ahead of time, the install instructions for the project are available here: http://docs.readthedocs.org/en/latest/install.html