VLC media player is arguably the best video playback software around. If you're a fan, good news: version 2.0.0 has been released in an impressive number of formats. In addition to a Windows installer, there are packages for OS X and multiple flavors of Linux. The code behind the open-source media player is available for download, as well.
As one might expect from an open-source release, VLC is available free of charge. It's also unsullied by the ads, toolbars, and other annoyances that plague a lot of free software. Plus, it plays just about everything. I've yet to encounter a video file that VLC couldn't handle, and this latest version brings support for even more formats, including Blu-ray movies and video encoded with 10-bit color.
Dubbed Twoflower, the latest version of VLC features a new rendering pipeline that purportedly offers faster decoding on multi-core CPUs, GPUs, and "mobile hardware." That last item may refer to devices like tablets and smartphones. Although version 2.0.0 doesn't appear to be available for those platforms just yet, VLC 1.1.0 can be downloaded for iOS. VLC for Android is in the works, too.
Twoflower's other new features are outlined on this page, which reveals that the release contains several hundred bug fixes contributed by some 160 volunteers—thank you, open-source community. That page has download links for the Windows and OS X installers. Linux users are encouraged to ask their favorite packager for VLC 2.0.