Chiming in a little late with some notes on watching the Olympics online.
Watching live:
If you can stay up late enough, you can watch all this year's judo matches live online. What a great luxury! Go to NBCOlympics.com, click on "TV & Online Listings", and follow instructions. You'll have to install a video plugin called Silverlight. It was simple and painless for me on my Mac.
Watching both mats at once:
The judo matches are happening on two mats. You can't use separate windows in your browser to watch both mats at once, or at least I haven't figured out a way. However, it is possible watch up to four live events at once, although at lower quality. Click on "Enlarge Video" and a panel of controls will appear on the left edge of the video. The top one of those controls lets you pick one main video and up to three other live videos to display simultaneously.
Watching later:
The judo matches start at midnight New York time and run to 8:00AM. If those times aren't convenient for you, you can watch some of the matches afterwards by clicking "Rewind". I don't know if NBC is planning to make all the matches available. As of this writing, Ryoko Tani's losing match is not available, and I'm really curious to see it. (I was actually watching live that night on two computers at once, one for each mat, but fell asleep. D'oh!) I'll probably check out the commentary on JudoForum when I get a chance; I'm sure there were some stunned reactions.
Another option for watching matches afterwards is to skip NBC altogether and go to Judovision.org. You could also search YouTube, though there's a good chance anything you're looking for is already on Judovision, and quicker to find there.
Gripes:
Unfortunately, all the videos in the simultaneous mode are smaller and fuzzier than when you commit to watching just one. And switching between them is not as snappy as I'd like — you lose a few seconds while the video is buffered.
You can't rewind a live event, so if you miss something exciting, you have to count on the instant replay or hope the match becomes available later in "Rewind" mode.
What I'd really like is if all the judo matches would be made available in high-definition, like some other events. I suppose I should be happy the matches are as available as they are.