Although there are lot of website available to track CTA (Chicago Transit Authority) bus movements ranging from CTABusTracker to TransitChicago providing you the up to the minute arrival information. CTA Bus Tracker uses GPS devices to find bus location data in real time.

Here is a beautiful Firefox addon to track your buses if you are using Chicago Bus Services as your transit. This addon works with Firefox 3.5 and higher versions and this version was developed by Joseph Booker.

So you can download this plugin here.