all of the above plus... (Score 1)

Of the stuff posted so far I'd say the best advice is subscribe to bugtraq read hacking exposed and the cryptogram news letter. plus.. SANS have shitloads of pretty decent stuff in thier reading room rr.sans.org Old issues of phrack contain really informative stuff like aleph1's 'smashing the stack for fun and profit' And Bruce Schneiers book 'secerts and lies' is quite good in a broad overview kind of way.