I am a linux newbie (openSUSE 10.3) on a Dell D600...I need to set this up to VNC into a number of RHEL4 servers. What is the tool to use on the laptop side?

Thanx.

You'll need a VNC Viewer running on the laptop
I am currently using xvnc4viewer, (but there are others).
xvnc4viewer IP.OF.SER.VER:displaynumber or
xvnc4viewer servername:displaynumber

Many KDE distros come with krdc (K Remote Desktop Connection), which is a GUI frontend to the above commands.
Obviously, you'll have to have a vncserver running on the server for this to work

Yeah, you're right about danger. The RFB protocol that VNC uses doesn't have encryption or secure authentication, which means that anyone might able to snoop on the connection and see exactly what you're doing on the remote machine, as well as impersonate you to connect to that machine in the future. Please do yourself a favor and use SSH. For servers, it's generally better to skip GUIs and stick to command line tools anyway. If you must use GUI tools, use X11 or VNC tunneled through an SSH connection. Again, please don't use an unencrypted protocol like plain RFB (for VNC), telnet, or FTP to administer remote systems unless you have complete control of the network and implicitly trust everyone who ever might be able to connect to it.