Yeah..........THis is a great place to learn about network defense and general security practices. If you want to learn to hack it dosent happen overnight and it actually takes years. If you want a place to go practice and not get arrested try some of the free online hack sites like www.hackthissite.org or some of the others. Good place to learn the concepts then expand on them and let your mind do the work.

One think I learned a long time ago is that most sites and people you find in the security arena ar not very open about teaching each other to "hack". Set yourself up with some reading and learn the basic concepts. If you can swing a few bucks to buy a book or 2 to get you started I recommend:

CounterHack Reloaded - Written by Ed Skouis - SANS Instructor and Incident Handler - Very good read if your new
Cisco Press: Penetration Testing and Network Defense

Search the web for:
Footprinting
NMAP Tutorial
Firewalk Tutorial
Enumeration
Those should keep you busy for a few days at least.