Convert from VMware VMDK to VirtualBox VDI

qemu-img convert image.vmdk image.bin

The resultant file will be a full-sized image, but sparse.

VBoxManage convertfromraw image.bin image.vdi --format=VDI

The resultant file will be a growable image, though it was significantly larger on mine than either the raw bin (allocated) or the vmdk.

Attach a raw (dd-style) disk image to a VM

First, attach it to a loopback device

# Linux
losetup -f disk.img
# FreeBSD
mdconfig -a -t vnode -f disk.img

Create a vmdk pointing to it

VBoxManage internalcommands createrawvmdk disk.vmdk -rawdisk /dev/loop0 # Or /dev/md0, wherever the image was attached

Remove the loopback

# Linux
losetup -d /dev/loop0
# FreeBSD
mdconfig -d -u 0

Edit the vmdk thus created, and change the path to point to the file

 # Extent description
-RW 2097152 FLAT "/dev/loop0" 0
+RW 2097152 FLAT "disk.img" 0

Make sure the two files are always in the same directory.

Attach to VM and test.

Configure VNC ext pack (4.2.6 OSE or later)

# Enable VNC extpack
VBoxManage setproperty vrdeextpack VNC

# Turn on VNC for a VM
VBoxManage modifyvm <name> --vrde on --vrdeport 5900 --vrdeproperty VNCPassword=password