Q: Can the new Apple TV stream media content from a first-generation Apple TV? It seems this would be a good alternative to leaving your computer on all the time.
A: The short answer is no. The first-generation Apple TV was never designed to be a media server for any device, and the new Apple TV is no exception in this regard. Further, Apple has basically discontinued the original Apple TV and stated that it will not be receiving any additional firmware updates. Since it is a discontinued product, Apple is not really expected people to use it as a host for content on the new Apple TV.
It’s also worth noting that the second-generation Apple TV uses the iTunes Home Sharing feature to connect to your iTunes library. Since this is an iTunes-specific protocol that requires authorization with an iTunes Store account, it is unlikely that the Apple TV will be able to interface with third-party media servers that provide iTunes sharing capabilities either. Essentially, your only option for streaming is iTunes 10.