OpenTripPlanner

OpenTripPlanner is an open source multi-modal trip planner released under LGPL. The software is at version 0.3 and currently implements:

Plans true multi-modal trips combining walking, biking and transit
Plans wheelchair accessible trips
Plans depart by/arrive by trips
Takes road type, bike lane, and elevation data into account when planning bike trips
Show elevation maps for bike trips
Imports data from GTFS, shapefiles, OpenStreetMap, and the National Elevation Dataset
Plans trips in about 100ms in a moderate sized city
Exposes a RESTful API (XML and JSON), which other apps or front-ends can build on