Browser Fairy - One tool to rule them all Get virtually as many default web browsers as you want.
CrossBrowserTesting - Browser Testing made simple! Run automated, visual, and manual tests on 1500+ real browsers and mobile devices. Test more browsers, in less time.
Choosy - Choosy opens links in different browsers as specified, according to rules, set by the user.
browserling - Live interactive cross-browser testing from your browser.
Account Surfer - Quickly switch between accounts and browsers on Windows
Browsershots - Browsershots makes screenshots of your web design in different browsers.