Below are links to a "few" of the most essential pages for someone who wants to get the best out of their iPhone. Any website listed is either an iPhone-related site or something I have found generally useful or interesting.

Gimp is not iPhone specific, but rather a GNU image manipulation program that will suite your image-inary needs. I have created all of my themes using Gimp, and I highly recommend, considering it is a free alternative to Photoshop.

BigBoss and the Dev-Team are two important figures in the land of jailbreaking, so I urge you to visit their sites as well. I have also listed certain tutorial sites and iPhone games that would suggest. Happy hacking!