kevinjardine/shoutout — Issue #5: Links are not auto-linked in the display
Author: mrclay
Created: 2012-01-10 21:18:13+00:00
State: open

This looks to be the best tool for this: https://github.com/jmrware/LinkifyURL/blob/master/linkify.js (or the PHP version)
The author seems to be a regex expert: http://jmrware.com/articles/2010/linkifyurl/linkify.html