IvoaTeX is a TeX-based software for authoring IVOA standards and Notes. Authors are encouraged to use it together with the IVOA-designated version control system *cough* github.
An IVOA note describing the system is written in ivoaTeX itself and can be cloned from github (if you believe you have the dependencies installed, building the document from there is a good idea; in general, checkouts will contain updates over the published Note).
IvoaTeX is designed to be included with the document source, preferably
via mechanisms of the version control system chosen (e.g.,
svn:externals or git submodule).
Still, in some situations it may be preferable to fetch tarballs of releases. Here they are:
[Version 1.3] [Version 1.2] [Version 1.1] [Version 1.0] [Version 0.4]
We used to have a crib sheet here; this content has now moved to the package's README.rst.