monotone is a free distributed version control system. it provides a simple, single-file transactional version store, with fully disconnected operation and an efficient peer-to-peer synchronization protocol. it understands history-sensitive merging, lightweight branches, integrated code review and 3rd party testing. it uses cryptographic version naming and client-side RSA certificates. it has good internationalization support, has no external dependencies, runs on linux, solaris, OSX, windows, and other unixes, and is licensed under the GNU GPL.
Codeville is a distributed version control system. It began with a novel idea for a merge algorithm and has grown from there. It is designed to be easy to use and scale from small personal projects to very large distributed ones.