Secure Shell (SecSH/SSH)

I've got a couple papers I've written about SSH.

Secure Shell (SSH): Advanced Techniques
This document describes some of the powerful functionality standard ssh (concentrating on the OpenSSH protocol 2 implementation) provides.

This is the paper you used to find at this URL. I needed to restructure things, so it went where the link above says.
Secure Shell (SSH): Security Considerations
And this one spends a bit of time discussing the security repurcussions implicit in standard SSH (protocols 1.5 and 2.0).

These are some documents relevant to SSH that I find particularly useful or interesting.

The SSH FAQ
The SSH FAQ is a great resource, even for advanced users. There are some incredible ideas there, such as running ppp over an SSH connection, providing a VPN.
OpenSSH
OpenSSH, the OpenBSD-sponsored implementation of SSH 1 and 2, as well as an sftp server running from inetd, is superb and completely free.
MindTerm
MindTerm is my second-favorite SSH implementation. It's a full-feature SSH1 implementation (v2 is in the works) in Java, with a nice GUI, good xterm-like functionality, with built-in scp and tunnel support. If you're stuck on a non-Unix platform to which OpenSSH is not portable, I'd recommend MindTerm. It's free and more feature-complete than commercial SSH implementations like SecureCRT.
Cygwin
While Cygwin isn't an implementation of SSH, it provides a build environment on the Win32 platform that allows you to build OpenSSH. Why use a crappy GUI client with limited features, that can't be used as your CVS_RSH or RSYNC_RSH when you can use a real, full-strength SSH?
SSH: The Definitive Guide
This is a book from O'Reilly, and the two chapters available are quite good.

ssh:mikehan.com