Are you looking for SSH (logging on to run command line programs) or SCP/SFTP (secure file transfer over SSH)? You said "SSH", but it sounds more like you want file transfer.
For file transfer only, if you don't require more than one user account, the CoreFTP
free mini-server works well and requires no installation or advanced configuration -- you can get it up and running in under a minute.
For anything more advanced, you can install OpenSSH following the instructions
here, which I've used before for reference myself -- it works well.
