Today, D.C.'s transit hounds get what once thought impossible: the Washington Metropolitan Area Transit Authority (WMATA; "Metro") is on Google Transit, a service that integrates maps and service schedules. It is available for dozens of other services worldwide.
So now it's possible to plot driving, walking and transit trips in the area. Other, smaller transit agencies had participated in the system, but not WMATA, which is by far the largest in the area, leading to absurd routings through remote counties on commuter buses. Or, more frequently, no option at all.
It's far from perfect -- one search I made suggested I ride one of those commuter buses for two stops; a five minute walk and wholly impractical -- to change to a Metrobus.
But it's service that I'll use, and hope Washington's visitors enjoy.