I'm going to have a look..
For stats and stuff... I've found the following interesting (for casual checks), although I'd personally want to check the sources if I was using it academically. They don't seem to have any equivalent of "purchase power parity" though. Also... I'm sure that many of the underlying stats are defined/gathered slightly differently in various countries - making comparison slightly risky.
http://www.nationmaster.com/
Having said that... it's fun to look at : >