Exchange 2010 beta is online
Wanted to test and play with Exchange 2010, go and get the beta from here https://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=1898ed2c-2f88-48ac-824e-d3d20fad77d7 also you can find the beta documentation at https://technet.microsoft.com/en-us/library/bb124558(EXCHG.140).aspx
Enjoy,