Normally I wouldn't bother to make a new article for this, but a lot of people were interested in the original post, and someone (Justus Stewart) finally sent in a link to a truly impressive transit-mapping application: Bus Monster.
Bus Monster hacks Google Maps to display nearby bus stops, the routes of whatever buses you care to look up, and when you click on a bus-stop bubble it shows you when the next few buses will arrive at that stop. You can even have it set an alarm to warn you a chosen number of minutes before the bus is due to arrive at that stop.
The tool is just a hack by Chris Smoak, but its interface is head and shoulders above anything else I've seen, including the professionally-built proprietary systems. The only problem is that it doesn't do trip-planning yet, which is a bit of a show-stopper. Also, it's custom-built for Seattle's online bus info, it's not universally applicable. But he says he's working on trip-planning data access, and he's going to open-source the code so others can do it in other locations. If all transit agencies used a single open-standard XML for input/output of trip data, writing the code once would make it work everywhere.
Okay, that's going on my site! As a veteran user of Seattle Metro's bus site, this is very useful.
Nice, but should add many features that have been available for some time on mybus.org ... or better yet, if anyone is still maintaining mybus.org, they should perhaps give it a facelift and include Justus' work!!
The bus listing at each stop are the right idea - but they aren't listed in the right order - they should be in the order of when they'll arrive, so you can see what your soonest options are.