We've been big fans of Google Transit since it came on the scene last year (unfortunately, it's not active where I live, or in nearly enough places. But it's a good start). The system was recently given a serious upgrade, and WorldChanging has got a nice walk-through of what's new and what's cool. The highlights: more cities, integration with Google Maps and Google Earth and the promise of more to come thanks to the GoogleTransitDataFeed open-source project (the FAQ still hasn't bee updated to include these changes). WorldChanging's Jeremy Faludi says that Google is providing all this data to users at no charge to the transit agencies. Very cool.
Google says that, "When transit data is integrated into products like Maps and Earth, it becomes even more valuable. Our hope is that placing transit information in the context of other useful information (like business listings) will inspire people to take public transportation who may have otherwise overlooked it."
[Source: Google Transit, WorldChanging]