Yesterday, on our sister blog WebWorkerDaily, I did a post on BlueOrganizer, a very handy extension for Firefox. BlueOrganizer lets you share content on del.icio.us, Twitter, and Facebook, but it really stands out in my eyes for allowing you to search laterally for content that is similar to what you're currently looking at. Here's more about it, including some illustrative screenshots.
I got the menu seen at left by right-clicking on a web page I was looking at. BlueOrganizer produces this menu to allow you to easily share content on social networks, or you can use the search features seen at the bottom of the menu here. Some people have called BlueOrganizer a semantic search tool. What it really does is identify what kind of content you're looking at, and then it searches Google and Yahoo for similar content.
For example, if I'm at a software-related web site and want to view other similar sites, I can rapidly have a Google search tell me what my options are. Alternatively, I can share content from the site I'm looking at on several popular social networks.

BlueOrganizer is also adept at letting you create its own style of Bookmarks. When installed, it puts a blue square icon on your Firefox toolbar. You can click it to bookmark any site, and add tags to your bookmarks, making it easy to get back to them in efficient ways later. You can also take a snapshot of text from a site and instantly embed it, in, say, a blog post. The bookmarking tool is seen at left, and note the Embed This option.
Especially if you search for information online a lot, this Firefox extension is worth trying. For many more useful Firefox extensions, see our superguide.