TinyURL Generator is a new experimental Firefox extension that makes it easier to grab a TinyURL of whatever page you're on. Once installed it will automatically create and save a smaller, shorter URL from TinyURL.com when new pages are visited. The TinyURL is then copied to your clipboard for easy copying and pasting in an e-mail or IM conversation.
For frequent TinyURL users this might be a better route than using one of the many available bookmarklets since it saves you a click and a copy/paste. On the flip side, it doesn't work so well when used in tandem with Web mail services because it will copy over the URL of your e-mail provider over the site you just visited. If you want to avoid that, be sure to have your Gmail, or whatever service you're using, open beforehand.
Update: As reader raggermany points out this is very similar to TinyURL Creator which also gives you a TinyURL for any page you're on. The big difference however is that TinyURL Generator converts links passively in the background.
Related: 10 links to shorten your links