Akos from the radioforeveryone.com blog has recently uploaded some new posts. The first post is a tutorial on setting up a PiAware server with an RTL-SDR. PiAware is the official ADS-B feeder software from FlightAware.com, which is a web service that provides real time tracking of aircraft. Most of the flight data comes from volunteers around the world running a PiAware server with an RTL-SDR, ADS-B antenna and Raspberry Pi. The installation is fairly simple, involves burning an SDcard with the PiAware image, setting up the WiFi and then seeing your receiver online on the PiAware website. From there you can then configure the device further.
In the second post Akos describes how to feed other tracking websites, e.g. not just FlightAware, but also similar sites like Planefinder.net and flightradar24.com. Akos has also mentioned that a single Raspberry Pi can be used to feed all three aggregators simultaneously.