vt52vnc is a VNC viewer which can be used on prehistoric green monochromatic terminals called vdt52s, which are capable of vector graphics. It is functional and nicely displays X on the terminal, but without the routines for dithering, compression, and password support. Its architecture provides a framework to add those features if needed.
Multixterm creates multiple xterms that can be driven together or separately. It can be used to login via SSH to multiple hosts and control them simultaneously, or for ad hoc things where you want to see the results as you type. Each xterm may also be driven separately. Multixterm is scriptable so that you can easily fire up, for example, a dozen xterms with a single command, tiled nicely on your screen. In addition to SSH, multixterm can drive rlogin, telnet, passwd, or any program that runs in an xterm.
S-terminal lets you create a secure X terminal. Regular X terminals pass unencrypted data between you the remote machine. S-terminal creates an encrypted tunnel through which all X traffic passes. It replaces the remote xdm login screen with a local application that collects username and password, then sets up an ssh tunnel to the remote host and starts a session. It is highly configurable both in appearance and behavior, and deployed S-terminals can be remotely administered. Best of all, it can be added to a KNOPPIX CD to create an instant, bootable, secure X terminal CD.