Basic dual monitor support is available under the Remote Desktop Protocol / Terminal Services. You must be running the RDP Client v6 or higher. You must run the command from either the RUN or CMD line interfaces. For frequent use you could always create a batch script which you can run from the desktop.
command:> Mstsc /span
For more information, see: http://www.microsoft.com/downloads/details.aspx?FamilyId=26F11F0C-0D18-4306-ABCF-D4F18C8F5DF9&displaylang=en