MockMockWeb is a Heroku-ready Node.js-based Web application server which allows you to mock up a website in seconds. It allows you to instantly launch a website which sends an empty page (with status 200) to any request/URL and edit any page on the spot. You can also edit the layout shared throughout your website. It lets you build a mock (sometimes real) website in a request-driven interaction.
cmocka is a unit testing framework for C with mock objects. There are a variety of C unit testing frameworks available supporting different platforms and compilers. Some development requires a lot of different compilers and older versions, which makes it difficult to use unit testing frameworks. The idea of CMocka is that a test application only requires the standard C library and CMocka itself to minimize the conflicts with standard C library headers, especially on a lot of different platforms.
ytest is a PHPUnit extension, based on the PHP extension "runkit", that allows you to replace static, private, and global functions with fakes, stubs, or mocks. This eases the automated testing of PHP applications that weren't written in a TDD fashion (i.e. test-first). It can also be helpful on projects where many methods are kept private, or projects that don't use OOP so much. ytest has already been used to "test after" (as opposed to "test first") some real-life commercial projects, and has proven useful. It needs PHP >= 5.2.