So I put this in hacking and security 'cause it just didn't feel like it fit into "found it on the webs"
All credit for this find goes to ChinkInArmor from IRC.
http://www.overthewire.org/wargames/is a site that tells you how to access a public "lab" for wargames. If you new to *nix, then start with Bandit level 0 and work your way up. In the bandit series you learn increasingly complex shell commands, and right off the bat you learn how to use SSH (as you can't do anything until you do
)
So far I've made it to bandit10, and honestly, it gets more complex real quick. From just learning how to ssh, to searching within a specified file of 1000 lines for a string of text that shows up only 1 time on level 9. Check it out, and happy hacking