Firefox Plugins which all work with the latest version of Firefox.

• Colorzilla – This one is great for graphic and/or web designers. Colorzilla lets you eyedropper sample any color code on any website in RGB, HSV and additional formats.
• Cooliris – If you are into graphics or photography, this is for you. Cooliris transforms your browser into a full-screen 3D wall for searching, viewing, and sharing images and graphics.
• Delicious Bookmarks – Adds buttons which allow me to easily bookmark pages to my Delicious account, which then feeds into my FriendFeed, which then posts to my Twitter.
• FoxyTunes – Adds play controls for iTunes to your browser’s status bar. Who wants to minimize their browser just to pick a new song? Now you don’t have to. Btw, if you are into the music network thing.. here are my last.fm or blip.fm profiles
• Screengrab – Does just that, in jpg or png format.
• StumbleUpon – Adds a toolbar, which I am usually not crazy about, but this one allows for very easy focused browsing of the web. You start a StumbleUpon account, enter your interests (i.e. web design, programming, and graphics) and then one-click browse away through related sites. I have my Stumble account linked to FriendFeed so I can share my “I like it!” pages via Twitter.
• Web Developer – Another toolbar yeah, I know : ( .. but suck it up (and/or disable it when not in use) Web Developer provides a great set of features for viewing html source code, dealing with forms, images, etc. However, I find the CSS editor to be extremely useful. You can split any page with css into two panes (one is the css and one is the preview), view stylesheet edits instantaneously, and then save the newly edited stylesheet. It’s really great for editing WordPress themes, or any theme for that matter.

Greasemonkey Scripts: first you download the Greasemonkey plugin.. then add the others.

• Greasemonkey – Allows you to customize the way a webpage displays using small bits of JavaScript.
• AutoPagerize – Eliminates the need to click “More”, “Next”, or any other page navigation on most websites… just keep scrolling down!
• Better FriendFeed – Displays extended user profile information on FriendFeed.
• Better Gmail 2 – (requires Greasemonkey) Enhances Gmail with a compilation of useful features like hierarchical labels, macros, file attachment icons, and more.
• Twitter Search Results - Displays recent relevant tweets in a short list before your Google search results