mad_maudlin has this linked at her LJ, but there's got to be a bunch of peeps I know who'll get a huge kick out of this!
This guy has put together
a visual comparison of the various starships throughout the best-known sci-fi genres, including Star Trek, Star Wars, the Stargates, BSG, Babylon 5, Farscape, and Firefly.
(On the large-scale diagram, Serenity looks teeny-tiny compared to the 1500m horror known as an Executor-class Imperial Star Destroyer...)