I use rdesktop on a Linux system.

If you are willing to install Red Hat Linux, you can find RPM at

http://rpm.pbone.net/index.php3/stat/4/idpl/888920/com/rdesktop-1.3.0-0.n0i.1.i686.rpm.html

http://www.rdesktop.org is the main website.

If your other machines are running Win9x or Windows 2000 then go to the following link http://www.microsoft.com/windowsxp/pro/downloads/rdclientdl.asp

This is a Microsoft remote desktop client for the older OS's.