SSH (Secure Shell) is a secure alternative to the ancient Telnet program/protocol. Telnet (and SSH) allows a user to connect to a remote server, and enables the users to use a command line interface to execute commands (manage the server).
Where Telnet is relatively limited in its functionality, SSH has a bunch of features which enables the user to do much more. The SSH protocol has the possibility to tunnel traffic through an SSH connection (read: tunnel). The big advantage is that everything going through the tunnel is heavily encrypted (which is good).

The tool best known to use SSH is SFTP (FTP over SSH). A secure alternative of the 'old' (in plaintext communicating) File Transfer protocol.
I tried to upgrade to OSX Snow Leopard today. 'Tried' is the keyword here. It seems though that the current installment of OSX (Leopard) is installed on a file system supposedly UNSUPPORTED by Apple OSX Snow Leopard.
NOTE: I have no way of knowing if the release I have is the final 'Gold Master'. So it could be that my findings are irrelevant for the actual (official) Snow Leopard OS.
I will however verify my findings when I have the actual 'Gold Master' in my possession.
When you run the installer from the OS (or by booting from the DVD) I get a error message saying that I need a GUID Partitione Table disk to install the new OS on. Somehow I use a different (and unsupported) partition scheme. And I thought that I selected all the best options during the clean install a while back......
There's no way of converting (using Disk Utility and/or Terminal commands) this to the appropriate settings without formatting your hard drive. So a normal upgrade is out of the question for me (or so it seems). And for many others I guess, since I won't be the only one with the 'wrong' partition table setup.
Since I upgraded from OSX 10.5.1 to 10.5.2 I haven't been able to use my shared printer on on my Windows server. Every job I submit gives me an error saying On Hold (Authentication Required).
There's no way that I could submit the printjob to the server from my Mac.
It seems that there is a bug in the authentication mechanism on OSX 10.5.2. If you add a (network) printer by using the System Preferences, you get to browse to find the actual printer.