There is an excellent site called TechNet Virtual Labs that enables you to quickly and easily evaluate Microsoft’s newest products and technologies via hands-on labs in which you are guided through the lab in about 90 minutes.
There is nothing to set up or install, as all the needed software is available via a Hyper-V session. All the products you will use are installed, configured, and ready to go. It’s the best way to play with a new product without having to create your own virtual machine and install a bunch of versions of trial software. And best of all it is free.
The 26 SQL Server 2008 labs are at TechNet Virtual Labs: SQL Server 2008.