Chrome only: Extension FastestFox adds a bunch of new options to Google Chrome to search multiple sites, add related links and turn text URLs into clickable links.
Once installed, you'll see a new icon in the toolbar that allows you to turn each feature on or off — including a new search box that allows you to easily submit your query to another service, hover search buttons when you select text, related links on Wikipedia, and turning text links into clickable links.
Once you've done a search, you can scroll to the bottom of the page, and FastestFox will load the next page below the current one on demand, so instead of clicking through every Google result, you can just keep scrolling. It's a useful extension that might be worth a look, especially if you spend a lot of time doing research. FastestFox is a free download, works wherever Google Chrome extensions do.