OSMExtracts

OTP includes a mechanism for automatically downloading OSM street data via the OSM API.

OTP can also load OSM data from a local file. There are several sites that prepare files containing OSM extracts for specific regions: http://wiki.openstreetmap.org/wiki/Planet.osm#Country_and_area_extracts

These OSM extracts, while much smaller than the full planet.osm, are still larger than a single city. You will probably want to crop them down to your area of interest using the Osmosis bounding-box task: http://wiki.openstreetmap.org/wiki/Osmosis#Extracting_bounding_boxes

PBF (protocol buffer) files are less voluminous than the older XML format. OTP can read them via the AnyFileBasedOpenStreetMapProviderImpl. GraphBuilder configuration for loading from a file (as opposed to region-based downloading) is covered in "Street Data" under the "Available Graph Builder Plugins" section of the GraphBuilder wiki page.