in combination with SFTP, as a secure alternative to FTP which can be set up more easily on a small scale without a public key infrastructure and X.509 certificates 

in combination with rsync to backup, copy and mirror files efficiently and securely 

in combination with SCP, as a secure alternative for rcp file transfers

for port forwarding or tunneling, frequently as an alternative to a full-fledged VPN.

In this type of use, a (non-secure) TCP/IP connection of an external application is redirected to the SSH program (client or server), which forwards it to the other SSH party (server or client), which in turn forwards the connection to the desired destination host.

The forwarded connection is encrypted and protected on the path between the SSH client and server only. Uses of SSH port forwarding include accessing database servers, email servers, securing X11, rdesktop, Windows Terminal Services and VNC connections or even forwarding Windows file shares

This is primarily useful for tunneling connections through firewalls which would ordinarily block that type of connection, and for encrypting protocols which are not normally encrypted (e.g. VNC)

for X11-forwarding for through multiple hosts 

for generally browsing the web through an encrypted proxy connection, using the SSH server as a proxy (with an SSH client that supports dynamic port forwarding) 

for automated remote monitoring and management of servers 

for securely mounting a directory on the server as a filesystem on the local computer, using the SSH Filesystem 

as a full-fledged VPN