[Thoughts on version control]
[The New Breed of Version Control Systems]
[On Arch and Subversion]
Arch
Arch distinguishes itself from the CVS/subversion model of versioning control by the fact that there isn't a single repository: every checkout kinda of create a new local and almost independent repository. You can do version control even without (net) access to the main repository.
SVK
[svk] is a decentralized version control system written in Perl. It uses the Subversion filesystem but provides additional, powerful features.