Windows/Mac/Linux (Firefox): Rather than search or hit "Back" to find a related link, the Fast Forward button asks you to rely on what other people jumped to next in their own browsing. The add-on adds a button to the right of your standard forward button (though it can be moved anywhere) which sends you to the most-visited page that other Fast Forward users headed to from the page you're looking at, or related pages if there's no exact match. The service doesn't require registration, but does ask for anonymised browsing data to do its thing. Currently, the app says it has 200,000 people contributing to its "most visited next" database. Reading through stories related to the troubles of Illinois' governor, Fast Forward sent me through an interesting mix of New York Times and Chicago Tribune articles, as well as a related YouTube video or two. Your mileage will certainly vary, but it's an intriguing, lighter-weight alternative to StumbleUpon and similar social browsing/bookmarking sitesFast Forward is a free download for Firefox 3 and works wherever that browser does.