Ihtml.vim is a project mainly written in Vim Script, it's free.
iHTML syntax highlighting
This is a mirror of http://www.vim.org/scripts/script.php?script_id=255
Does "smart" highlighting of all iHTML syntax. Handles up to iHTML Enterprise Edition 2.20. Also highlights SQL within SQL= attributes (which you can turn off if you'd like). If you're using foldmethod=syntax, there are some nice folds setup by this syntax file.
Latest version always available here: http://www.markfeeney.com/resources/ihtml.vim