Thursday January 19, 2012 at 3:13PM from Biztrails T.
From the airport to the city,

Even if it isn’t on the cutting edge, public transport in Chicago is efficient. Using the CTA Blue Line, you can travel from the airport to the city and/or back. You can buy day tickets, 3-day or 7-day tickets (currently the 7-day ticket costs $23.00). There are ticket machines located in the airport terminal at the entrance to the platforms. These seasonal tickets provide hassle-free transport on all CTA trains and buses. Using these services, you can get to practically all the interesting places in the city. Compared to the single fare tickets at $2.25 (train) and $2.00 (BUS), the 7-day ticket is a real deal.