Did you know that Chicago has a number of Farmers Markets that run roughly from May until October? Some are sponsored by the city, and some are independent.

For a list of all neighborhood markets, with dates, visit Explore Chicago's Farmers Market Page.

There's four downtown locations, two on Tuesday and two on Thursday. I wish they had them on Wednesdays, which is the day I'm most likely to be downtown.

Originally from here but with some additions...

Adler Planetarium
September 7, 13-17, 21, 28

Art Institute of Chicago
The Art Institute of Chicago is free to the public every Thursday evening from 5pm-8pm

Brookfield Zoo Free
The Brookfield Zoo offers free admission to all U.S. Armed Forces active military and reservist personnel

Chicago Children’s Museum
Free for everyone – Every Thursday evening, 5-8pm
Free for ages 15 and under – First Sunday of every month

Chicago History Museum
Free Days 2010: Every Monday, 9:30am-4:30pm

DuSable Museum of African American History
September 4th

Field Museum
September: 13th, 15th, 16th, 21st, 22nd

Lincoln Park Zoo
Free to the public 365 days per year

Museum of Contemporary Art
Every Tuesday of 2010, 10am – 8pm

Museum of Contemporary Photography
The Museum of Contemporary Photography is Free every day of 2010

Museum of Science and Industry
September 7-14, 20-21, 27-28

National Museum of Mexican Art
Every Tuesday-Sunday

The Peggy Notebaert Nature Museum
Every Thursday, 9am-4:30pm

The Oriental Institute Museum
Free admission, suggested donation of $7.00

Shedd Aquarium
September 13-14, 20-21, 27-28

Swedish American Museum
September 14