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