Once you've updated to 3.0.6, check out the VirtualBox Web Console as described here. Within some minutes, you should be up and running. Still a lot of work to do but there are some useful features that you can enjoy today:
- Browse your virtual machines and inspect their settings
- Start virtual machines in headless mode
- Pause/resume VMs
- Save the state of running VMs
- Terminate VMs (hard power off or ACPI)
- Remote control your VMs using the integrated RDP Web Control
A lot of limitations still like no authentication for the RDP viewer. You will also find a Create VM wizard which is not fully done yet but gives you an idea of what to expect in the near future.