VirtualBox 3.1.0 Beta 1 was just released. This is a major update bundled with quite a few cool and much anticipated features. The release also includes bug fixes for version 3.0.10.
Teleportation (Live migration) – You can now move VMs across machines.
2D video acceleration for Windows hosts.
Snapshot got smarter. You can now restore from any snapshot and not just the last one.
Network modules can now be changed while the VM is running.
Performance improvements for PAE and AMD 64 guests.
For the complete list of changes please check out the change log.