To join in from your Mac or PC, just go to the next page by clicking the link at the bottom of this post, and you'll find a live stream viewer and a chat tool.
If you're driving somewhere and would like to watch TUAW TV Live while you're stuck in traffic, please don't -- keep your eyes on the road. However, if someone else is doing the driving, you can watch the show on your iPhone by downloading the free Ustream Viewing Application.
iPad users haven't been forgotten. You can tune in the show on your iPad now by clicking this link, which will open a non-Flash stream. Huzzah!
Last-minute panic note: it appears that Ustream's chat tool is coming up slowly this afternoon. Be patient, and eventually you'll be able to join the chat.