Most Metra (Chicago's commuter rail service) riders live near a station that they use to ride a train into the city. Metra's online schedule tool does provide upcoming train times, but it requires entering the time you plan on departing and your selections aren't bookmarkable. My tool provides an extremely barebones interface to first select a train line and stop, then display the amount of time until the next train coming in each direction. And of course, it is bookmarkable.