Wine is an implementation of the Windows API on top of X and Unix. It does not require Microsoft Windows, but can use native Windows DLLs if they are available. It provides both a development toolkit for porting Windows source code to Unix as well as a program loader, allowing many unmodified Windows programs to run on x86-based Unixes.
minor feature: Built-in implementation of cryptographic hashes. Mono engine updated with upstream. More Direct3D command stream work. Simulated bold and italic in DirectWrite. Improvements to the XML reader. Various.