Mesa 3D is a collection of graphics libraries and drivers that implement hardware-accelerated OpenGL 3. It comes with its own software emulation fallback driver though. Besides OpenGL and OpenGL ES, it implements OpenVG and EGL, but also allows for Direct3D interfaces.
VirtualBox is a full x86 hardware virtualizer, suitable for server, desktop and embedded usage. It's extremely feature-rich, emulates lots of individual and alternative hardware and devices, supports different virtual machine disk formats, it's cross-platform and supports ancient and current Windows versions, DOS systems, BSD, Solaris and OS/2 as guest operating system.
Clone, build, run ... Linux from scratch with TroglOS ARM Versatile based virtual devboard
Wine Staging is a testbed Wine compilation with new experimental features and application bug fixes (formerly known as wine-compholio). It's synced with regular Wine, and patches sent upstream after testing. There are for example CSMT, or CUDA/PhysX support, DXVA2 GPU video decoding, Job Object support, named pipe message mode, IO performance optimizations, S3/DXTn support, the threadpool API, d3dx9 improvements, Windows ACL support, and a PulseAudio driver for Wine.