Are you still trying to catch up with what’s new in the 5.1 release of VMware ? perhaps a quick overview is what you need, from then on you can look into the different enhancements based on your interest focus.
I have found two great resources for people wanting to get a high level overview of 5.1 and what’s new.
Firstly, a great video shot by VMware here:
Secondly a pdf giving you an overview of the new release details which can be found here: http://www.vmware.com/files/pdf/products/vsphere/vmware-what-is-new-vsphere51.pdf