I just built a 3 node cluster with its own AD domain on VirtualBox last week..
Windows 2008R2 Enterprise
3 Cluster Nodes
1 AD DC with MS iSCSI Target 3.3 software.
Built one on VMWare workstation 5.5 about 3 years ago.
I have been trying to get VMWare server to run stably on my machine and have had trouble. I also did basically the same thing as above with Windows 2008 Enterprise and the filer as Windows 2008R2 Standard running MS iSCSI Target 3.3.
Like all things cluster for MS SQL shared storage was the only hitch I ran into.