VirtualBox

VirtualBox is partially libre, gratis virtualization software.

VMware Support

While VirtualBox should be able to open .vmdk images, if your version is unable to, you can crack open VMware images with dd. See the VMware article for instructions.

Converting a Raw Image

To convert a raw image to a VirtualBox dynamic image, you just need to run the VBoxManage convertfromraw command.

$ VBoxManage convertfromraw centosroot.img centosroot.vdi
VirtualBox Command Line Management Interface Version 3.1.0
(C) 2005-2009 Sun Microsystems, Inc.
All rights reserved.

Converting from raw image file="centosroot.img" to file="centosroot.vdi"...
Creating dynamic image with size 2829464064 bytes (2699MB)...