NAnt-completion is a project mainly written in Vim Script, it's free.
XML omni-completion data for NAnt build files
This is a mirror of http://www.vim.org/scripts/script.php?script_id=1820
File to allow Vim's xml autocompletion to work with NAnt build files (http://nant.sourceforge.net/). Elements and attributes were taken from the 0.85 version schema.