As much as NBC's TV coverage can be biased and annoying, their official web site is a fantastic place to watch events live. You won't see everything there live -- I think they hold off the events they'll end up showing in prime time, like the swimming and gymnastics events -- but that's sort of the point of this site. This is where you can go to see the sports you can't see on TV.
I'm not a huge fan of the format, if only because you're required to download Microsoft's Silverlight plugin. There's nothing wrong with it, per se -- it's basically just a Flash analog, as far as I can tell -- but I dislike having to install extraneous programs on my computer. I already have Flash on it; why do I need something else?
And the coverage is strangely addictive. Even more bare-bones than the Triplecast, the webcasts are little more than live feeds of events, with score and point graphics, but without any commentary. Which, I have to say, I love. It's fascinating how utterly irrelevant most sports play-by-play is; we're just used to it. Yes, I personally need it for football (which is incomprehensible without it, thanks to its Byzantine collection of field rules), but nearly evey Olympic sport there is can be deciphered easily on your own.
Weightlifting, for example, which I'm watching right now. It couldn't be simpler: keep lifting heavy things over your head, until you can't any more. It's the womens' 75+ kg clean and jerk (that's how much they weigh, not how much they're lifting; at this point they're well above 150 kg), there's nobody telling me the life story of the woman from Uzbekistan, no cutting away from some random competitor, and no commercials. It's fantastic.
Seriously, I would pay money if my TV coverage was like this. Heck -- I did pay money in 1992. I would do it again gladly.
And the woman from South Korea just set a wold record by jerking 186 kg over her head. For the metrically disinclined among us (like me), that's 310 pounds. Wow. I feel a soliloquy to the wonders of the human body coming on.