Know when that bus is coming? You could write an app to tell you, if you live within the service areas of these innovative transit authorities.
TriMet (our TriMet API profile) leads the way with open data. As a Portland resident, I may be biased, but don't take my word for it. When Google wanted to provide transit-based directions, it turned to TriMet to set the example for what is now a standard format.
Now TriMet has over 25 apps built by local developers. In addition to scheduling information, you can access real-time stop wait time data, which means more accurate apps.
BART (Bay Area)
The Bay Area Rapid Transit (our BART API profile) trains connect downtown San Francisco with many surrounding cities, including Oakland. The API provides XML feeds of station and train data, updated every minute.
Like TriMet, there are a number of example apps listed in the BART developer section.
The result is an programmer interface that shows the CTA what's important. As Reed says: "The power is not the mashup. It's the data."
King County (Seattle)
Again, it's not exactly official, but a research group at University of Washington has worked to give Seattle's transit an API (our King County Buses API profile). In addition to schedules, developers can also access real-time location data of every bus, as showcased in their BusView applet.
Should your transit authority be on this list? Let us know in the comments, or add its API.