Developers usually do a great job of writing installation guides, or building automated installers. However, they typically do a lousy job of explaining how to remove software. In the OSX/*nix world, this can be a real pain because executables, libraries, configuration, and other files are usually dispersed across your filesystem. Tools like Homebrew do a great job to combat this by giving a user a central place to install and remove software.
Below are links to some uninstallation instructions for various popular software on OSX: