It looks that CE does have a good ssh client (POCKET PUTTY
[You must be registered and logged in to see this link.] which turns our netbooks to console clients. Then, for graphic environments you need X Window server, running on the terminal (client
side.
There are several free X Window Xorg compliant servers running upon MS Win 32 of different versions. They use either cygwin (http://x.cygwin.com) or mingw (sourceforge.net/projects/xming/), there is also an implementation, which links to VS runtime libraries and even a Java applet implementation (http://www.jcraft.com/weirdx/). If any of those environments had been fully ported onto CE, one would be able to recompile it here. WeirdX one might be interesting, since it won't need special recompilation, if we have some good Java VM.
Again, those we need to have a thin client for Linux's. On the other hand, IT IS a thin client for windows, since it's ready to connect to windows boxes thru RDP right now.
IMHO, VNC may be a good choice, since it's an open remote access protocol with tons of server side implementations running on different OS's.