This is a good list - though not exhaustive, it's certainly got many of the better known ones:
In David Weber's Dahak series, Earth's Moon is actually a starship.Niven and Pournelle's Ringworld is actually a starship.
I noticed on Wikipedia that one spacecraft design envisaged as part of Project Orion would have been 1,300 feet wide and weighed approximately 8 million tons, while being potentially big enough to host a city of 100,000 or more people. How does this proposal compare with other starships (fictional or real design studies) in terms of size?