Tools / Library
Nothing... and again.. NOTHING can beat an extensive library on reef topics. The Internet can be great for gathering information. However, bulletin boards and email lists aren't really all they're cracked up to be. No one really cares to hold your hand ;) As well, once you've gotten the knack of things, it's also good to go back thru and see if there's some clue to a mystery you're trying to solve.
Figure 1