Description (in their words): CoRD is a remote desktop client for Microsoft Terminal Services servers. This means you can connect to a computer running Windows and control the computer remotely.
Although I've only been using this software for about 2 days, I find it very affordable (free) and very powerful (if you use RDP). It works better than MS RDP for Mac OS X. Just give it a try and you'll see what I mean. You can actually play around with the RDP connection windows, where in MS RDP you are severely limited to what you can do. It also renders the remote desktop 10 times better than MS RDP.
Give it a try.