Smartmockups - Create stunning product mockups, easily and online.
browserling - Live interactive cross-browser testing from your browser.
AppLaunchpad - Create free beautiful screenshots for App store/Google play
Browsershots - Browsershots makes screenshots of your web design in different browsers.
Placeit - Generate realistic product shots in seconds
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.