This is a small script to linkify urls, email addresses, and twitter handles in a string, extracted from the twitter widget at http://wmnf.org.
The code is mostly from http://stackoverflow.com/questions/37684/how-to-replace-plain-urls-with-links/7123542#7123542. There are other, more extensive solutions out there, notably https://github.com/cowboy/javascript-linkify.
Example:
text.linkify()