Here are a list of headless browsers that I know about:
- [HtmlUnit][1] - Java. Custom browser engine. JavaScript support/DOM emulated. Open source.
- [Ghost][2] - Python only. WebKit-based. Full JavaScript support. Open source.
- [Twill][3] - Python/command line. Custom browser engine. No JavaScript. Open source.
- [PhantomJS][4] - Command line/all platforms. WebKit-based. Full JavaScript support. Open source.
- [Awesomium][5] - C++/.Net/all platforms. Chromium-based. Full JavaScript support. Commercial/free.
- [SimpleBrowser][6] - .Net 4/C#. Custom browser engine. No JavaScript support. Open source.
- [ZombieJS][7] - Node.js. Custom browser engine. JavaScript support/emulated DOM. Open source.
- [EnvJS][8] - JavaScript via Java/Rhino. Custom browser engine. JavaScript support/emulated DOM. Open source.