VirtualBox 4 available for download, adds extension support, disk resizing
The new option to create .vbox shortcuts is a real convenience, as it allows you double-click (or single, depending on your preferences) launching of your favorite VMs. Windows, Linux, and Solaris guests can also now auto-mount shared folders, which makes it easier to access files on your host system.
Oracle has also polished up the VirtualBox UI with improvements such as a sortable VM list. Hit up the changelog for full details about the new release.
Download VirtualBox 4