I agree with blogosphere consensus that Marc Andreessen is a pretty great addition to the world of blogging. It was the following post of his that really gave me quite a bit to think about: the examples are pretty solid, but the source material: this essay on "The Psychology of Human Misjudgement" by Charlie Munger is absolutely fascinating.!
It took me a while to get through it, but the points are great reminders about the biases all of us have, and the mistakes we so very easily make. Chances are you've probably read many of these before and/or thought about them, but they're a great collective reminder of psychological mistakes you (or others) make and how to correct them.