Total number of items: 25

• Adblock Plus 0.7.5.3
  http://adblockplus.org/
  Firefox 1.5 – 3.0b5pre
  Ads were yesterday!
• Better GReader 0.2.2
  http://ginatrapani.org/workshop/firefox/bettergreader/
  Firefox 0.8 – 3.0b4
  Enhances Google Reader with Greasemonkey user scripts.
• ColorZilla 1.0
  http://www.iosart.com/firefox/colorzilla/
  Firefox 1.0 – 3.0a2
  Advanced Eyedropper, ColorPicker, Page Zoomer and other colorful goodies
• Copy Plain Text 0.3.3
  http://mozmonkey.com/
  Firefox 0.7 – 2.0+
  Copies text without formatting
• del.icio.us Bookmarks 1.5.44
  http://del.icio.us
  Firefox 1.5 – 2.0.0.*
  Access your bookmarks wherever you go and keep them organized no matter how many you have.
• Digg Firefox Extension 0.4.3
  http://www.tc.umn.edu/~wilm0044/digg/
  Firefox 1.5 – 3.0b4
  Allows you to interact with Digg and see information about the web page you are currently viewing while you use Firefox.
• DOM Inspector 1.8.1.12
  http://www.mozilla.org/projects/inspector/
  Firefox 2.0.0.12 – 2.0.0.12
  Inspects the structure and properties of a window and its contents.
• Dust-Me Selectors 1.1
  http://www.sitepoint.com/dustmeselectors/
  Firefox 1.5 – 2.0.0.*
  Finds unused CSS selectors
• Extension List Dumper 1.12.0
  http://sogame.awardspace.com/
  Firefox 1.5 – 3.0b4
  Dumps a list of the installed extensions.
• Firebug 1.05
  http://www.getfirebug.com/
  Firefox 1.5 – 2.0.0.*
  Web Development Evolved
• FireFTP 0.97.1
  http://fireftp.mozdev.org
  Firefox 1.5 – 2.0.0.*
  FTP Client for Mozilla Firefox.
• FireShot 0.36
  http://screenshot-program.com/fireshot/
  Firefox 2.0 – 3.0b4
  Adds the ability to take a screenshot of the page, edit it and save, copy to clipboard, send to external editor or e-mail it.
• Gmail Manager 0.5.4
  http://www.longfocus.com/firefox/gmanager/
  Firefox 1.0 – 2.0.0.*
  Gmail accounts management and new mail notifications.
• Google Toolbar for Firefox 3.0.20070525W
  http://www.google.com/
  Firefox 1.5 – 2.0.*
  Take the power of Google with you anywhere on the Web!
• IE View 1.3.6
  http://ieview.mozdev.org/
  Firefox 1.0 – 3.0b3
  Open pages in IE via Firefox menus
• MeasureIt 0.3.6
  http://www.kevinfreitas.net/pro/extensions/
  Firefox 0.9 – 2.0.0.*
  Draw out a ruler to get the pixel width and height of any elements on a webpage.
• Operator 0.9
  http://www.kaply.com/weblog/operator/
  Firefox 2.0 – 3.0b4The Semantic Web in Action
• Password Exporter 1.1http://passwordexporter.fligtar.com
  Firefox 2.0 – 3.0b5pre
  Export and import your saved passwords.
• Remember The Milk for Gmail 1.0.1http://www.rememberthemilk.com/services/gmail/
  Firefox 2.0 – 3.0
  Task management goodness.
• ScribeFire 1.4.7http://www.scribefire.com/
  Firefox 2.0 – 3.0b4
  A full-featured blog editor that integrates with your browser and lets you easily post to your blog.
• StumbleUpon 3.17http://www.stumbleupon.com/
  Firefox 1.0 – 3.0b5pre
  StumbleUpon Toolbar
• Tails Export 0.3.2https://addons.mozilla.org/extensions/moreinfo.php?id=2240
  Firefox 1.5 – 2.0.0.*
  Extension for Showing and Exporting Microformats.
• Text Area Word Counter 1.2http://ginatrapani.org/workshop/firefox/textareawordcounter/
  Firefox 0.8 – 9.9
  Counts the total number of words in all the textareas in a document.
• Web Developer 1.1.5http://chrispederick.com/work/web-developer/
  Firefox 1.0 – 3.0b4
  Adds a menu and a toolbar with various web developer tools.
• Slow 0.9.4http://developer.yahoo.com/yslow
  Firefox 1.5 – 3.0b4pre
  Make your pages faster with Yahoo!’s performance lint tool.

It shares a lot of the same concepts as the Last.FM app but the look and feel of how well it integrates with iTunes is impressive. I really like how it fits in as a sidebar instead of a separate GUI and lists recommended artists (with previews), links to free mp3′s from up & coming artists that are related, videos, tourdates and news all from within a seamless interface.

As far as cool goes, These go to 11.