...and possibly anyone else who cares.
Firstly, you must read
The Worst DM Ever. For extra fun, read the DM's
rebuttal.
Treasure Tables is absolutely priceless (although most of the content is DM-oriented). Be sure to check out their
forums.
Errant Dreams has some more player-oriented stuff, particularly about character development and the like. Both of these sites have really good articles on not only how something can mess up a game, but also why it does so.
In terms of general play aids, you absolutely *need* to have
The Hyptertext D20 System Reference Documents bookmarked. This is basically a well-formatted presentation of all the rules WOTC released under the OGL. Need to know how a spell or a feat works? Two mouse clicks away. Absolutely priceless.
If you want a character generator, I really like
PCGen. It can be a bit slow and fiddly (a consequence of being written in Java I'm afraid), but it is *very* powerful and flexible. Plus, it's open source, which gives it even more awesome. ;-)
Also, check out
Crystal Keep, which has indexes of pretty much any WOTC published crunch.
Lastly, for a little bit of fun, check out this
thread over at EnWorld discussing the phenomenon in 4e they're calling "Schroedinger's wounding". :-)