i'm choosing to ignore the hacker crap as it offends me and annoys me.. but i will give you some info..

I take it that you do not have copious numbers of computers to experiment with, making networking experimentation more difficult, although not impossible.. if you are looking to move to a Linux distribution, and do not currently have much experience but would like to change that.. Redhat or SuSE would be a good choice, as they allow you to experience linux without forcing you to be very familiar from the start. However, if you do have unix-like-os experience, and would like a suggestion as to a good system to learn, the above suggestion of the BSD's are good, FreeBSD is somewhat userfriendly while still requiring a fair amount of experience to use effectivly, OpenBSD would be the OS i would choose for more server experimentation, as it is by default very secure, lightweight, and has a good userbased support community behind it.

As you were vague to your requirements, i cannot focus any of my comments towards specifics. But if you would like to get into computer security, i would suggest reading and experimenting with ipv6, and/or ipsec, encryption, and general network security using firewalls and security policies.

good luck, and i hope that someday you outgrow your hacker fixation..