I've written up a guide for using Arch with OpenACS:
http://www.rubick.com/openacs/arch
This is a limited use of Arch -- it is not a CVS <-> Arch gateway, which is the holy grail of version control.
However, this does let you check out the stable releases of OpenACS, make local modifications, and deploy them in a staged process that allows you to test changes before taking them live.
Bear in mind I wrote most of this from memory, so there are likely some errors. Please email me with additions.
Eventually, I'd like to get some sort of Arch documentation into the official documentation, but I'd like to get it right first.
