There have been alot of starhips of all manner of size and shape through the anals of science fiction film and TV. Somehow Dan Carlson has created a series of Starship Size Comparison Charts showing all our favourite ships together from the small to the gargantuan.
The images/files are great - go there for the goodness , this is the sort if super geekiness that everyone can enjoy.
Plus there is Jeff Russell's Starship Dimensions site which has a staggering array of ships, creatures and more at various scales.
Plus check out the Starship Schematics site for more.
[few schematic images from the Starship Schematics site]