VirtualBox command-line interface (VBoxManage) provides an easy way to convert raw disk image to the VDI/VMDK format and otherwise.

Let's assume that we have raw image of the sdb device:

$ sudo dd if=/dev/sdb of=./sdb.raw

To use it with VirtualBox we need to convert it to the VDI format:

$ VBoxManage convertdd sdb.raw sdb.vdi --format VDI

To use it with VMware we need to convert it to the VMDK format:

$ VBoxManage convertdd sdb.raw sdb.vmdk --format VMDK

Convert between VDI/VMDK formats:

$ VBoxManage clonehd sdb.vdi sdb.vmdk --format VMDK

$ VBoxManage clonehd sdb.vmdk sdb.vdi --format VDI

Convert to the RAW image:

$ VBoxManage clonehd sdb.vdi sdb.raw --format RAW

Alternative solution to get back raw image after applying modifications is to use qemu-img command from qemu package:

$ qemu-img convert -f vmdk sdb.vmdk -O raw sdb.raw

Now we can write image to the device:

$ sudo dd if=./sdb.raw of=/dev/sdb