Where to start?

Hello everyone,

I'm looking forward to a career in the security field.  Specifically, I'm 
interested in Pentesting.  I concider myself "early" in my education, and have 
alot to learn, but my biggest concern is, where do I need to start?

I mean, what do I need to learn about to become a pentester, and where can i 
gather and explore my knowlage?

In order to not leave this question TOTALLY OPEN, I'll give a quick background 
of what I know so far.

I'm currently enrolled in classes to learn to be a Network/Server Admin, 
including classes in Cisco, Basic Hardware and Microsoft Servers.  I currently 
hold certification for CCNA 1&2, and hope to get 3&4 in June of this year.
Also, I have a linux server, and a couple of linux VM's that I've been learning 
on.  And I'm fiddling with "C" right now to get a basic background in 
programming.  But with the knowlage I have, I don't think I could offer any 
value in a pentest.  I've done some port scans of various, random IPs (sorry if 
I gave any of you a scare at work :), and I've seen open ports, but I dont' 
know what to do next...

So, what information do i need to study to start getting a grasp of what I 
would be doing in my job?  (other than just start hacking random computers, 
which I'd rather not do)

I appreciate your help,
Michael