http://www.openssh.com The home page of the OpenSSH implementation of SSH that Fedora Core Linux uses. It is run by the same team as OpenBSD, a secure BSD-based operating system.
http://www.realvnc.com The home page of the team that made VNC at AT&T's Cambridge Research Laboratory. It has since started RealVNC Ltd., a company dedicated to developing and supporting VNC.
http://www.tightvnc.com Here you can find an alternative to VNC called TightVNC that has several key advances over the stock VNC release. The most important feature is that TightVNC can use SSH for encryption, guaranteeing security.
http://www.nomachine.com/ Another alternative to VNC is in the pipeline, called NX. The free implementation, FreeNX, is under heavy development at the time of writing but promises to work much faster than VNC.
One book on SSH that stands out from the crowd is known as "The Snail Book" because of the picture on the cover. It covers all the SSH suite and is called SSH: The Secure Shell (O'Reilly), ISBN: 0-596-00011-1.