Chicago has two major airports: The O'Hare International Airport and the Midway ariport.
If you are arriving in Chicago by plane, there is a convenient public transportation (L-train) provided by the Chicago Transit Authority (CTA) , that will get you within a walking distance from the main venue of the SIGMOD/PODS conference.
From the O'Hare airport, you need to take the blue line train and exit at the Clark/Lake station. Walk north for 1 block until you intersect the Wacker Drive (across the bridge) and then walk west 2 more blocks. If you arrive at the Midway airport, take the orange line train and exit at the State street station. You are only 1 block (going north) away from the hotel.
At this time, the fair for the L-train is $2.00. You can check an up-to-date information about the trains' schedules and see the maps at the CTA's web site .
At both airports, there is always an abundance of taxi-cars available. The transportation price to/from the Renaissance hotel is approximatelly $35.00.