This plugin highlights the matching HTML tag when the cursor is positioned on a tag. It works in much the same way as the MatchParen plugin.
It was inspired by this question http://stackoverflow.com/q/8168320/20388.
The latest 'release' is available on vim.org.
Other file types
To get this to work for file types other than html that use a similar tag structure (e.g XML) you can do something similar to this.
echo 'runtime! ftplugin/html.vim' > ~/.vim/ftplugin/xml.vim
The xml.vim file demonstrated here is included with MatchTag.
Thanks to ithaca.arpinum.org for this screenshot.