jsFiddle Integration with forum
I often use jsfiddle to learn and draw up new ideas using jQuery.
http://jsfiddle.net/
It may only be in alpha but it is already very powerful and easy to use and share.
Maybe have the ability to use the embed link to show your jQuery in action? The default method is iFrame. Maybe input the ID of the fiddle and PHP can build the actual iFrame to display so users cannot abuse adding iFrame's themselves.