"Paver is a Python-based build/distribution/deployment scripting tool along the lines of Make or Rake. What makes Paver unique is its integration with commonly used Python libraries."
Paver is lacking many features that Capistrano has, but it is Python. Currently supports only Subversion for remote deployment (no word on Python-powered tools like Mercurial yet) and other interacting with remote machines is virtually nonexistant.
Not quite there yet, but Paver has lots of potential. I'd love to switch from Capistrano to something like Paver at some point.