Power Twitter is an add-on for Firefox that takes regular Twitter and gives it mag wheels, a spoiler and a brand new engine. 

After installing Power Twitter and restarting your browser, your Twitter page will have these new features:

1) inline embedded media from Flickr, YouTube, TwitPic and others
2) expanded URLs so you can see where links might take you
3) twitter search and search results right on the page
4) peek – an avatar mouseover that lets you see recent tweets from that person
5) status updates that are happening with your friends on Facebook
6) when possible additional web updates (Flickr, blogs, etc.) for certain users

Power Twitter is yet another great free contribution to the Twitter community from very talented developers.

Find out more about it at http://83degrees.com/post/Adding_Features_with_Power_Twitter

TwittyTunes is a browser extension for Firefox and IE that lets you easily Tweet whatever you are listening to at the time.

In addition, you can also Tweet the websites you visit, and the videos you watch.

To be able to Tweet the songs you are listening to, you’ll need to have FoxyTunes installed.

Otherwise, you can still post about websites, videos, and general updates. Take a look, and listen, to TwittyTunes at http://www.foxytunes.com/twittytunes/