Windows Remote Desktop (RDC) from OSX/Mac
These are two clients for connecting to a Windows Terminal Server (Remote Services) or any other Windows machine (7/Vista/XP/2003/2008) that may have remote desktop access enabled over port 3389.
The official Microsoft client for the Mac/OSX is version 2.1.0 at the time of this writing and available here: http://www.microsoft.com/mac/remote-desktop-client
Many users have complained about the stability and reliability of the MS client, as an alternative there is an open source solution called CoRD with much better reviews: http://cord.sourceforge.net/