Boxee is a 3rd party software that you install on the Apple TV via a USB Mem Stick. Boxee has (had) the ability to stream from multiple internet sources such as Hulu, Joost, CBS and Comedy Central. However, Hulu has recently been on the warpath, pulling their content from lots of different places (Boxee and TV.com to name two). At this point, there is no way I know of for streaming fox, nbc shows to your ATV. You can stream CBS, Comedy Central and soon, ABC. However whether all this content will stay on Boxee is now a big question mark after the crap Hulu just pulled.
If the internet sourced content dries up, Boxee will most likely be DOA.