The Qt 4.8 libraries were made available today for Windows, Mac OS X, and Linux oprating systems. The full Qt SDK update for 4.8 isn't coming until January, but today's release does bring several new features as a step towards the Qt 5.0 release next year.
Qt 4.8 introduces Qt Platform Abstraction (what was the Qt Lighthouse Project) for a clean abstraction layer to port Qt to new windowing systems, Qt Quick improvements, Qt WebKit is updated to version 2.2.1, and there's threaded OpenGL support.
The Qt Platform Abstraction in 4.8 and Qt 5 is what makes it easier to port this open-source tool-kit to other platforms like RIM's QNX (Blackberry), Android, and Wayland. The threaded OpenGL support for Qt should also be great.
The release announcement for Qt 4.8 can be found in this Nokia blog post.
Digia, the firm handling the commercial version of this tool-kit, also announced the commercial version compared to the LGPL version of Qt 4.8; there's "108 improvements and bug fixes available in Qt Commercial 4.8.0 that are not part of the LGPL release."