Create and transfer SSH public key then login to remote machine in one step:

$ ssh-keygen; ssh-copy-id user@remotehost; ssh user@remotehost

Copy ssh keys to remote host to enable password-less ssh logins:

$ ssh-copy-id user@remotehost

Start a tunnel from remote machine’s port 80 to your local port 8888:

$ ssh -N -L8888:localhost:80 remotemachine

Compare a remote file with a local file:

$ ssh user@remotehost cat /path/to/remotefile | diff /path/to/localfile -

SSH connection through host in the middle:

$ ssh -t reachable_host ssh unreachable_host

Copy from host1 to host2, through your host:

$ ssh root@host1 "cd /somedir/tocopy/ && tar -cf - ." | ssh root@host2 "cd /samedir/tocopyto/ && tar -xf -"

Run any GUI program remotely:

$ ssh -fX <user>@<remotehost> <program>

X11Forwarding should be set to "yes".

Attach screen over ssh:

$ ssh -t remote_host screen -r

Have an ssh session open forever:

$ autossh -M50000 -t remotehost 'screen -raAd mysession'