Please do NOT use this VirtualBox Beta release on production machines. A VirtualBox Beta release should be considered a bleeding-edge release meant for early evaluation and testing purposes.

You can download the binaries here.
The packages are currently being uploaded.

Please do NOT open bug reports at http://www.virtualbox.org/wiki/Bugtracker but use our VirtualBox Beta Feedback forum to report any problems with the Beta. Please concentrate on reporting regressions since VirtualBox 4.0.10.

VirtualBox 4.1 will be a new major release. The following major new features were added:
Support for cloning of VMs (bug #5853)
GUI: enhanced wizard for creating new virtual disks
GUI: new wizard for copying virtual disks
VMM: raised the memory limit for 64-bit hosts to 1TB
Windows guests: Experimental WDDM graphics driver
Guest Additions: modules and features now are represented as facilities to have a common interface for frontends.
New Networking Mode: UDP Tunnel. Allows to interconnect VMs running on different hosts easily and transparently, see the manual for more information.
In addition, the following items were fixed and/or added:
VMM: more SMP timer fixes
VMM: fixed sporadic recompiler crashes with SMP guests
VMM: many small fixes
GUI: when reverting to a snapshot, ask for taking a snapshot of the current state
GUI: added View menu
GUI: added setting for the promiscuous mode policy for internal networks, bridged networks and host-only networks
GUI: the VM description is editable during the runtime of a VM
GUI: added proxy settings (bug #2870)
VBoxManage: changed syntax of the guestcontrol command group, fixed various bugs
VBoxBalloonCtrl: new service for automatic dynamic adjustment of the balloon size for running VMs
Settings: machine names and snapshot names are not allowed to be a valid UUID
Storage: virtual CD/DVD images will be detached if the guest ejects the medium
Floppy: several bugs have been fixed
BIOS: disk-related structures are now checksummed correctly
USB: many fixes for the Windows USB host driver
NAT: reduced memory footprint
Serial: announce the serial devices in the ACPI tables to make Windows guests find the virtual hardware (bug #7411)
VRDP: support for TLS connections
VRDP: support for multimonitor client configurations with MS RDP client
3D support: fixed GL_VERSION string for different locales (bug #8916)
Windows hosts: fixed copy'n'paste in the GUI and for the VM window (bug #4491)
Guest Additions: improved driver installation on Windows guests
Guest Additions: fixed high CPU usage while executing guest programs from the host