Odds are Nintendo is going to go THREE DEE for their DS today, allowing you to get all three of the dees in a portable package. You can watch their unveil live.
Here's Ustream's, which should be live shortly before the presentation starts (at 9am PT)
If you want Nintendo's own stream, in case Miyamoto throws out some F-bombs and they have to bleep bloop it out before it hits your ears, then head here.
But if your work blocks Nintendo.com, then you can hit up YouTube's stream, though I don't see what kind of work would block Nintendo but not YouTube.
Don't forget Kotaku's live coverage as well.