In an earlier blog post, I showed how to install ESXi as a virtual machine for testing purposes. This is one of the fundamental steps to building a virtualization test lab to play with features of vSphere.
Another fundamental step is configuring some sort of shared storage for an ESXi host. This can be done using software storage products such as StarWind, Openfiler, FreeNAS or Nexenta. Many of these are available in free installations as well. Of course this can connect to hardware SANs that present storage over iSCSI as well.
This gallery will walk you through adding iSCSI storage in a lab capacity for vSphere.