World Economy Historical Statistics [warning .xls file!]

economy > statistics >historical

This large table contains basic estimates of Population, GDP and GDP per capita for most countries since, umm... 1 AD, but getting more detailed from 1500 onwards and dense by 1900. Use it as a reference, a source for an (obscure) argument about economics, or to create hardcore trivia questions (I'll take "Asian Economy in the year 1500 for 1000, Alex").
Found through following successive links from nationmaster, which has added historical world economy data to its statistics (see this for example) and is quickly developing into the internet statistics benchmark.