browserling - Live interactive cross-browser testing from your browser.
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.
BrowserStack - BrowserStack is a software testing platform for developers to comprehensively test websites and mobile applications for quality.
Ghostlab - Ghostlab allows you to test out a newly developed website on a variety of browsers and mobile devices at the same time. To get started, simply drag the web address to the Ghostlab system and press the play button. Read more about Ghostlab.
Browsershots - Browsershots makes screenshots of your web design in different browsers.
Browsersync - Browsersync makes your tweaking and testing faster by synchronising file changes and interactions...