You can also use the BBCode built into the forum if that's where your wanting to shorten urls.
For example you have this http://www.superlongneverendingurlth...oonforever.com
Will display this in your actual message:Code:url=http://www.superlongneverendingurlthatwillgoonforever.com]Linked Text[/url]
Linked Text
Note the example in the "code" box has the first bracket [ removed otherwise it would just have linked text in that box also so you need that first bracket [