go to http://www.try2hack.nl hacker  and see how far you can get! This site is alittle old but there is still many that have never tried it so go ahead and see if you can do it.

Slimjim100

If you enjoyed this my I suggest:

http://www.hackergames.net/ is a big list of similar sites my favourite was http://www.hackthissite.org some fun challenges there most but not all hacking related, nice "real world" senarios, and logic puzzles. Lost a lot of sleep with that one. If memory serves there were about 50~60 challenges.

As with most of these sites you'll get a mix of idiot script kiddes and very helpful people using them. (not all whitehats, you have been warned)