As I am sure you are all well aware one of the ways that Microsoft makes our software available for testing is through the use of trials.  Here is a list of the current trials i would recommend using and the links to download each of them. 

Windows 7 Enterprise 90-day Trial    

Download the Windows Server 2008 R2 Trial Software

Evaluate Forefront Server Security Management Console today

Download Microsoft System Center Essentials 2010 Beta Today

Evaluate System Center Virtual Machine Manager 2008 R2 today

Evaluate Windows HPC Server 2008 

Of course if you are interested in pushing your test and trial machines to another level you could also Sign up for the TechNet Plus Subscription using the discount code TNITE02 and save $97 off the regular price of $349. 

Have fun Trying out the latest and greatest stuff!