VirtueMart is a very huge feast indeed. There are dozens of extensions available to make it work more effectively and to adapt it to specific applications. If you feel the need to get more out of your VirtueMart installation, visit the page created for these specific extensions at http://extensions.joomla.org/extensions/extension-specific/virtuemart-extensions, and dig in as much as you like.
"Joomla! E-Commerce with VirtueMart" by Suhreed Sarkar is also a great book from Packt Publishing in which you will learn topics such as: