VirtualBox 2.2.0 was released this morning with OpenGL 3D acceleration for Linux and Solaris guests. Additionally, VirtualBox 2.2 supports importing and exporting appliances from the Open Virtualization Format, a host-only networking mode has been introduced, various Hypervisor optimizations, an elevated VM memory limit for 64-bit guests to 16GB, VT-x/AMD-V are enabled by default for newly created virtual machines, and USB is enabled by default on new virtual machines. When it comes to Sun's operating systems, there is now experimental USB support for OpenSolaris hosts and shared folders for Solaris and OpenSolaris guests. Additionally, VirtualBox now has a C API in addition to its Java, C++, and Python interfaces.
The release announcement with download links for VirtualBox 2.2 can be found on the project's mailing list. Additionally, the VirtualBox 2.2.0 change-log is available on their Wiki.