I've done or seen the following done with spare DirecTV dishes:
1) sell the feedhorn on ebay for about $10
2) re-aim the dish and feedhorn to a satellite offering free-to-air or similar service
3) replace the feedhorn with something appropriate for 802.11, and experimente with long-distance WiFI
4) installed a 1691MHz feedhorn, downconverter, etc, and built a GOES/MeteoSat geosynchronous weather satellite reception station.
5) As #4, but add azimuth and elevation motors so that you can pick up the hi resolution pictures from polar-orbiting NOAA satellites on 1701MHZ
6) get an FCC (or equivalent) amateur radio operator's license and operate a 1296, 2304, or 3456 Mhz propagation beacon.