Penn World Tables (PWT)
The Penn World Tables offers "purchasing power parity and national
income accounts converted to international prices" to make meaningful
international comparisons. It covers roughly 170 countries with about
30 time series from 1950 to 2000. It has a very flexible system
for retrieving data. You can select variables in various ways and have
it put into one of three different types of files: HTML, SAS, or csv
(comma separated values -- they are easy to bring into spreadsheets).