ShortMe is a Safari and Google Chrome extension which lets you short long urls in your input fields.
This URL Shortener extension has been designed to be used in the Twitter’s site, Google Maps, Gmail and Facebook Chat. It’s also for all other website which contains an input box.
Resources

versions
1.0.3
- URL selection is easier. Only need to right-clic on the URL without a whole selection
1.0.2
- [chrome] remove button in tool bar
- [chrome] remove permission for files access
- [chrome] fix bug when page contains frames (works in GMail now!)
1.0
- first version
- support for Safari and Google Chrome