Link 1: Windows 7 Test Drive [This will link you to 7 virtual machines, one of which will be running Windows 7 Ultimate] on a time limited demonstration basis: 35 minutes I think.

The demo did not seem to start properly but the window asking if it is OK to connect to the remote machine appeared as a pop under and so I did not notice it at first.

Other resources on this page:

Link 2: Download details: Deploying Windows® 7 Essential Guidance from the Windows 7 Resource Kit and TechNet Magazine

Other test drives:

Link 3: Windows 7 Test Drive; IT Pro; Greater Productivity

Link 4: Windows 7 Test Drive; IT Pro; Enhance Security and Control

Link 5: Windows 7 Test Drive; IT Pro; Streamlined PC Management