Very simple Vim functions to toggle comments for c, c++, Python, shell scripts, and Erlang files.
Just add the files or the functions to ~/.vim/ftplugin directory.
The keys mapped to toggle comments are [CTRL]_ (that's control + underscore) and can be changed easily.
Currently, only one comment type is supported at a time. If a different file type is loaded in the same Vim session, then a warning is given and the keys are not remapped. I'll be looking into making it smarter in the future as long as it stays simple.
Available on vim.org (http://www.vim.org/scripts/script.php?script_id=5458)