HaX.ToR.Hu is a challenge site putting emphasis on teaching basic security related issues in a fun way.
Players get a free shell account to use (with web/mail hosting) on a server (with gigabit bandwidth) dedicated to security folks.
A few examples of HaX.ToR challenges:
Level 1. Make a nasa.gov URL display a text of my choice
Level 7. snifflog.txt - ngrep format
Level 13. PHP with source - needs exploiting and/or
Level 16. root:hsmfs;email@example.com
Level 21. Backdoor on a suspended domain
Level 26. PHP filemanager with source - needs more exploit
Level 28. telnet://hax.tor.hu:1800 - Google Word Game
Level 33. Defense Information Systems Agency - 188.8.131.52
Level 39. China Science And Technology Network
Level 40. I can has satellite?
Level 48. .htaccess editor vs basic auth
Level 49. Forged DNS from the CIA