This link has a list of all of NBC's live online streams, as well as streams of past events.
What's cool is, you can join a live stream halfway through the event and start it from the beginning, like it was on your DVR. Same thing with streams for events that are over.
And they don't post the scores on this screen if you don't want to know the results.
It also has a full schedule of all events to be streamed in the future. Pretty cool.
You can also sign up to have it send you a text when an event you are interested in is available as a stream.