Absolutely, positively guaranteed to entertain you, or possibly blow your mind. (not a guarantee)
www.peterwood3d.com - The home of my brother, a very talented 3D artist, musician, game designer, and the most imaginative person I know.
Formerly, there were links to two news sites here. I have since made up my mind that news is not worth knowing, and I would not want to exacerbate the problem by spreading anymore knowledge of current events. Seriously, current events are like .00000000000000001% of all that is interesting about life and the world. If something really important happens, such as a nuclear war, or the rise of some 4th Reich, I can assure you that you'll hear about it through other means.
www.sysopmind.com - A site that hosts the various writings of Eliezer Yudkowsky. This young prodigy has an unusually persuasive way of writing about unusually exciting things, including The Meaning of Life, programming, cognitive science, Bayesian reasoning, writing itself, the future, but most of all: Real Artificial Intelligence.
www.homestarrunner.com - The funniest flash cartoon site on the entire internet. Don't go there unless you have about 15 hours to kill.
www.theinquirer.net - Not what you might think. This is the best and most up-to-date site for computer hardware news.
www.ocremix.org - A fantastic and enormous collection of well-produced remixes, in every imaginable style, of VIDEO GAME MUSIC. If you're into clever music, look no further. For the most part, the recordings are professional quality, or damn near close.
Near-Death Experiences - I am not a 'religious' person, per-se, but I've had first-hand encounters with things that seemed a lot like "God," heaven, hell, conscience, judgement day... so at the very least it seems that there are enormous forces at work in individual and collective human psyches. The 8 billion accounts and essays on this site are fascinating, and will give you plenty to think about. Which parts are "true" and what "truth" is are completely separate matters.
www.moller.com - What....? Did you think flying cars were still science fiction? Uh uh. They're in development.
Google Maps - This used to be a link to TerraServer, but that has clearly been supplanted.
www.topcoder.com - A site that hosts regular tournaments for programmers. For money.