I'm not finding many links for streaming video of this year's 24 Hours of Le Mans but I'll try to update throughout the day with any links I do happen to find.
Speed TV: Speed will be providing a live video stream when they are not broadcasting the race on TV. The stream will be active from 12:00 PM to 4:30 PM and 10:00 PM to 12 Midnight EST. This feed may not work if you are not in the US. To view their live TV broadcast on your computer, you can try the TVU Player.
Justin.tv: If this video feed stops working, try doing a search for "LeMans" or "Le Mans" in the upper right hand corner of the Justin.tv website to find another channel.
Radio Le Mans: A live audio feed. Click the "Listen Live" button in the upper left part of the homepage.