Oracle VM VirtualBox (formerly Sun VirtualBox, Sun xVM VirtualBox and innotek VirtualBox) is a virtualization software package for x86 and AMD64/Intel64-based computers from Oracle Corporation as part of its family of virtualization products

Since VirtualBox-4.3.8-4 PLD package, you can autostart guests:

1. edit /etc/vbox/autostart.cfg and fill which users may access the feature
2. as user, configure autostart dbpath:

   $ VBoxManage setproperty autostartdbpath /etc/vbox/autostart

3. modify VM to enable autostart of it. (use VBoxManage list vms or VBoxManage list runningvms to figure out the UUID or VM name):

   $ VBoxManage modifyvm <uuid|vmname> --autostart-enabled on