A while ago, I saw a fanatic excel sheet that detailed all the corporations in the Sixth World (I believe there might have been a similar thing detailing locations, as well). Now that I’d like to refer to the information, my Data Search skill has failed me.

If this sounds familiar, could someone point me in the right direction?

Ah, finally found it. It was an extended test.
Its' Nath's Corporate Index 2065. This fine piece of work (and worthly of a plug!) is located at:

http://nmath.free.fr/onyx/depot/?D=A

Now, am I crazy to think there was a similar thing covering geographic locations?
Say, if I wanted to look up all references of Prague or Saint Louis?

That would be the Sixth World Wiki. It grew out of Wordman's Sixth World page where he summarised and indexed all the different country information from the various sourcebooks up until he decided to stop and then after a brief interval it was converted into a wiki hosted by the nice people here at Dumpshock so anyone could help maintain and contribute to it. Unfortunately it got hit by some major vandalism just recently and Adam hasn't had a chance to look at fixing it due to being fairly busy and real life intruding.

Oh, that's VERY nice! Thanks for the link!