Currently we have the "< php >" tags and the highlighting is generated 'server side'.

With forums where syntax highlighting is extensively used, it would not only be nice to offload the server to the client side (php vs javascript), but to also add more than just php code as that being highlighted.

There are .js libs out there to do the trick and they fall into various categories. Most important of which is licensing (FREE to use and add to commercial product).

Two products (and there probably are more) that come to mind are:

http://softwaremaniacs.org/soft/highlight/en/ (ty Ian)
http://code.google.com/p/syntaxhighlighter/

both fit the 'FREE' category. one being a short license blurb allowing it and the other with a full on GNU Lesser glob.

This would be simple to add to the <? button as a dropdown to generate the appropriate class tags, allowing for all kinds of highlighting that is accomplished on the clients' machines.

Thanks to Ian Spence for this idea.