TechNet virtual labs are a great way to evaluate and test Microsoft's newest server products through a series of guided, hands-on labs which can be completed in 90 minutes or less. There online and FREE.
We've just added some new V-Labs for Windows Vista, Exchange Server 2007, 2007 Microsoft Office System (including the new UI improvements in Windows SharePoint Services 3.0). This really is a great resource in that it enables you to try out these products without having to set them up on a test system.
You can try out these v-labs for yourself here.