Tab Candy for Firefox
Here is a fun tech toy in development called Tab Candy I ran across through the ALA email list. This Firefox browser extension allows you to nest (create sub tabs) and visually control the myriad of tabs you have open on your web browser. Even though it is still in beta, you can download it and test it, or you can wait until the final product release. This is definitely a resource to keep your eye on — it may someday become a standard feature on most web browsers.
Aza Raskin’s blog does a great job of describing what you can do with this tool.