UltraVNC

There is just one button on the viewer, but it does what you set up on server. I use VNC in school too, and I have just unchecked Enable Blank Monitor on Viewer Request in properties window on the server. So if you don't like to use monitor blanking at all, this is a solution for you.

On the other ...

I'm using RemCom for controling remote PC. Command remcom \\machine cmd launches interactive console session. (Equivalent to telneting to remote host)

Pros:
Uses Windows authentication
No remote installation needed Cons:
Connection isn't secured nor uses existing winvnc session
You need SAMBA ...