This is a small mootools automcompletion tool.
Takes an input field, an URL called via Ajax - or a javascript function to provide the completion values.
http://www.chipwreck.de/blog/software/cwcomplete/demo/
http://www.chipwreck.de/blog/software/cwcomplete/help/
See http://www.chipwreck.de/blog/software/cwcomplete/help/ for more information.