Ask HN: Best Tool for Sharing Developer Notes, Processes, etc

We are a small startup that has added 3 developers in the past 6 months. Life is still good. Developers have a lot of autonomy, and we are still sharing most of views, thoughts, processes by email, IM, phone or in-person. However, the transitory nature of those communication channels is beginning to cause a problem.

What tools are startups using to share persistent information between developers?

We have tried using basecamp but everything gets buried in messages. The important stuff does seem to bubble up to the surface.

We tried dropbox and google docs but there is no separation between personal and startup. Plus its a mess.

We thought about standing up a wiki but I'm not very enthusiastic. It seems like creating technical documentation.

The best option I have found is crowdbase but I thought I should search HN to see if it has been discussed previously. I couldn't find anything which has triggered me to ask, what are other startups doing?