KwiClick may be one of the best productivity boosters for Firefox you'll ever use. This add-on delivers instant information from popular sites and services, such as Amazon, Flickr, Google, Twitter, and YouTube. It does it for free, and with little more than a click or two.
When you're on a Web page, highlight any text, and a small clover icon composed of four smaller icons appears above it. Each icon represents a Web site or service. By default, the four services in the clover are Google, Wikipedia, YouTube, and Google Maps, although you can customize that. Click one of the icons, and information from the selected site appears in its own small pop-up window inside the current window, where you can then interact with it--click to search results, view a video or photograph, and so on. KwiClick makes it easy to branch out your browsing without losing the page that piqued your interest.
KwiClick arranges icons for other services across the bottom of the window, so that you can quickly get information from one of them as well. You can pin the window to Firefox so that it's always visible, or else close it.
There are far more options available, too many to include in a short review. You can customize the clover icon with a variety of sites, use a variety of shortcut keys for how to open the KwiClick window (in a new tab, a new window, and so on), to name a few. It's a very useful feature, particularly if you favorite search and information sites you check frequently. Simply add them to the clover, and you'll be able to get to them from KwiClick without having to navigate to the sites themselves to do searches.
The upshot: If you use Firefox and often look for information from multiple sites, you'll want this excellent free add-in.