ColorZilla is a great extension for Mozilla’s Firefox web browser. The main feature here is the ability to get a hex color reading straight from the browser and into your favorite photo editing program. HIGHLY RECOMMENDED!

2. Aardvark

Another great Firefox extension that allows you to see exactly how a web page is contructed, block by block. Mouse over effects include: element type, css classes, IDs, and more!

3. Wikimedia Commons

A huge collection of free images, photography, sound, and multimedia. All of the content is either in the public domain or released under free licenses such as the GNU Free Documentation License.

4. Adobe Labs: Kuler

Allows you to view, create, and save various color schemes.

5. Browser Shots

Generates screenshots of how websites appear at 800×600 and 1024×768 resolution in 6 commonly used web browsers.