Convert from QEMU raw and VirtualBox VDI (...and viceversa)

From RAW to VDI:
qemu-img convert qemu.img qemu.bin
VBoxManage convertdd qemu.bin qemu.vdi
VBoxManage modifyvdi qemu.vdi compact

From VDI to RAW:
VBoxManage clonehd "qemu.vdi" "qemu.img" --format RAW