While iPhone users benefit from built-in transit directions, iPod touch users can feel left out on the curb.
However, until the iPod touch incorporates transit directions (and I hope it will), there is another option — UniBus for iPod touch and iPhone. Unibus is a $1.99 app that allows you to look up arrivals and departures for many transit systems that make their GTFS publicly available, including those of two Trillium clients, agencies in Humboldt County, California, and Mountain Line in Flagstaff, Arizona.
Since the schedule information is downloaded to the device, network access is not required to lookup schedule information.
More information is available from the UniBus website. Below, a screenshot of the app.