For Museum of Science and Industry (and Frank Lloyd Wright Robie House in Hyde Park), the Metra Electric Line (www.metrarail.com) is more pleasant and faster than the bus, though you have to walk about 3 blocks. Get off at 55th/56th/57th Street, exit at the southern end of the station, and turn left. A couple of excellent bookstores (Powell's and O'Gara and Wilson) are within 2 blocks west (the other way) on 57th.

Same line takes you from Millennium Station to Museum Campus (second stop) for Field Museum and Aquarium, but it's only 1.5 miles, so a cab is better. Or it makes a nice walk in pleasant weather.

Metra has a $5 weekend-long pass (unless they raised it, which they were talking about).