XfreeRDP can be used to access cluster based on windows 2008 technologie.
It is avaialble in SLC distribution as well as on the website : http://www.freerdp.com/
OBSELETE :Rdesktop installation for Linux
Important note :
rdesktop does not support windows 2008 cluster.
A seperate public cluster called rdesktopts has been set up to allow rdesktop user top connect but xfreerdp should be prefered.