Older buildings have higher floors. See how old and new buildings connect via stairs.
A list of elevators (under construction).
Other small oddities that aren't worth a full page:
Building 54 (Green Building) has a tall first floor because the Cambridge building codes restrict number of floors but not height.
Using underground tunnels, you can get from Mass Ave to building E25, right next to the T station (from 8 go 16 to 56 to 68 and then follow signs). There are also no connections between dorms and this system because of a rule (MIT's or Cambridge's) that dorms and labs cannot be connected via underground tunnels. They had some trouble getting the tunnel under Ames St approved by Cambridge (see the Tech article); one under Mass Ave would be even harder I bet. I call this whole tunnel system the underground infinite corridor. In addition a tunnel was once planned from E18 to E15; going under Ames St you can see where it would be. The floor plans show this as a future knockout wall to E15. However E15 (the media lab) didn't want the tunnel and so it goes nowhere.
Between buildings 2, 4, 6, and 8 is a courtyard only accessible from the basements. This is known as the "secret ninja courtyard" (officially the Atomic Courtyard, room 6-024). There is also a secret ninja parking lot between 1, 3, 5, and 7; this is also accessible by road obviously (the road that crosses the basement of the infinite corridor).
There are several patterns in the lines of buildings. On the west is 1-5-7-9-33-35; the next vertical line is 4-12-24-34, and the next one is 2-6-8-16-26-36. The 2 horizontal lines are 7-3-10-4-8-16-56-66-68 (infinite corridor) and 35-37-39-38-34-36; some patterns are evident (8-16-26-36 for example). Of course there is also the even-odd pattern (odd west of the center line (10-13-39) and even east), which only 57 violates.
Of course there is also a whole lot of hacking locations. I do not plan on listing them here for obvious reasons.
Please email me at [email protected] with any additions or corrections. Some of this info is thanks to Jack Florey, which he told me on the way to Baker House. Also thanks to David Maze for info. There are also very nice floor plans at floorplans.mit.edu (accessible only from MIT), and a red book in the reference section of the Rotch Library (2nd floor of 7/7A) has several that aren't included in the website, including roofs and former building 20.
My main website is the SPUI Freeway, which deals with roads, mainly FL, NJ, and Boston.