Not too approximately: Even numbered buildings are to the east of the central grassy plaza (Killian Court), and odd numbered buildings to the west; the numbers tend to increase moving away from the river.

Additionally, buildings outside the main cluster have a cardinal direction prefix (W/NW/N/NE/E) that helps locate them.

<http://whereis.mit.edu>

(I know you know all that; I'm adding context for the readers.)

I have to admit I never noticed the even/odd rule. Maybe I'd have found Building 2 without having to look it up the other day :-)