I\'m looking for an on the fly URL shortener much like how tweetdeck works. I have found many jQuery and general javascript plugins that take a url and run it through a shor
I found your post while looking for something similar and eventually just wrote a jQuery plugin that provides (at least part of) what you're looking for.
My jQuery Url Shortener on Bitbucket
It's a very simple plugin; I didn't need to shorten the user's urls so I don't have any length checking or url testing before shortening it, though I am not averse to adding those types of features.
Just thought you might find it useful.
As for Recognising URLs in your textbox, I would suggest using a RegEx to match the url.