To understand what hackers are talking about, you'll need to speak their language. The Hacker Jargon File can help. Real, live hackers gather once a month for the local meeting of 2600, the club for hackers. All the meetings are scheduled for the first Friday of the month between 5 pm and 8 pm local time. In Philadelphia, the meeting is held at 30th Street Amtrak Station at 30th & Market, under the "Stairwell 6" sign.
Famous author Bruce Sterling has been very kind and released, for free, the complete text of his book The Hacker Crackdown, the story of governmental efforts to combat hackers. One organization which was investigated by the government was Phrack Magazine.
From Technology Review, April 1995, comes an article by Wade Roush: Hackers: Taking a Byte Out of Computer Crime.
Fen Labalme has put together a page of Hacker & Cypherpunk Resources, and Eric S. Raymond has written a page on How To Become A Hacker. Scott Vogt wrote a paper: Hacking On The Internet.