* "-D" for ssh tunneling.
* "-L" for forwarding all traffic on a specific port.
* sshfs - mount small directories over ssh on your local machine (works with big ones but way too slow, for big ones I go rsync).
* "-R" for reverse forwarding on a specific address.
That is, you can connect from the remote host to your local network. I used to do this to make my system at home accessible on my workstation in the office :) if you don't specify the address to forward to you will get a SOCKS proxy on the port specified that tunnels connections to your local network.
It is also possible to forward non local ports but ports on machines accessible to the side that is forwarding too.