Like the LAPD scanner link I posted week or so ago, this link to LiveATC.com lets you listen in to that is happening at Van Nuys airport as aircraft arrive and depart. Van Nuys is the business general aviation airport in the US, so there is always a lot going on. You can also listen in on what other aircraft, like LAPD, are doing near the airport, as they need to stay in contact whenever working in the Van Nuys airspace. Van Nuys is also the base for LA County Fire Helicopters.
This feed could also be useful if you happen to visit the Van Nuys Airport Observation area off of Woodley Avenue. Using your iPhone or other mobile device, you could listen in on traffic as you watched the planes arrive and depart. When my son was younger, we used to visit here so he could watch the airplanes up close.
Link: Van Nuys Ground and Tower – KVNY radio feed via LiveATC.com