Similar or related tools

bumpversion is the original project off of which bump2version was forked. We'll be merging back with them at some point (issue #86).
tbump is a complete rewrite, with a nicer UX and additional features, like running commands (aka hooks) before or after the bump. It only works for Git repos right now.
ADVbumpversion is another fork. It offered some features that are now incorporated by its author into bump2version. This fork is thus now deprecated, and it recommends to use bump2version (issue #121).
zest.releaser manages your Python package releases and keeps the version number in one location.
setuptools-scm relies on version control tags and the state of your working copy to determine the version number.
incremental integrates into setuptools and maintains the version number in _version.py.
Invocations packaging.release are a set of tasks for invoke. These assume your version is in _version.py and you're using semantic versioning.
python-semantic.release automatically bumps your (semantic) version number based on the types of commits (breaking/new/bugfix) in your source control.
PyCalVer is very similar to bump2version, but with support for calendar based versioning.

Change log building

towncrier assembles a changelog file from multiple snippets found in individual (merge) commits.
releases helps build a Sphinx ReStructuredText changelog.
gitchangelog searches the git commit history to make a configurable changelog file.