if you already play a fundmental poker game, and are profiting, theres not much else.
However, there is one book I found to be quite excellent.
Killer Poker Online
http://www.amazon.com/exec/obidos/tg...books&n=507846
<disclaimer: there is no amazon affiliate link here
This is a personal recommendation, I make no profiit if the book sells.>
This book doesnt tell you how to play differently, but it explains how your game is effected by online play.
It's very good, if you like to understand why you act the way you do while playing, and how to tweak your tendencies to make more profit.
Whatever you can to get that "edge"
I highly recommend it.