A mindblowing compendium of science fiction spacecraft! at merzo.net:

This site is intended to allow science fiction fans to get an impression of the true scale of their favorite science fiction spacecraft by being able to compare ships across genres, as well as being able to compare them with contemporary objects with which they are probably familiar. The scales are based on meter-to-pixel ratios so that they are accurate on any platform.

The spacecraft are presented in a variety of different scales on a massive piece of virtual graph paper. If you’re using Internet Explorer, you can even pick up the ships and move them around. Finally, you can back up that “The Enterprise D would totally kill the SDF-1!” claim with hard-hitting information graphics! You would still be wrong, even with Transwarp, but at least your argument would have some surface credibility :-)