You can take Windows Vista Ultimate edition demo online for free. You can actually use and explore a lot of features of Windows Vista in the demo. The features are categorized in four categories as safe, easier, reliable and versatile. Under these categories you can view and explore new interface, Internet Explorer 7, instant search, Windows BitLocker drive encryption and many others. Advanced user can explore features like remote desktop, group policy, account, firewall management etc.

Although, you require good Internet speed to see Windows Vista in action but this is really cool. check it out.