Here's a list of useful links that will help you learn all about open data and assist you in developing great apps:
City of Sydney open data portal - datasets available to the public for general information, for the wider benefit of the community, and to encourage an accessible and connected city.
Data.gov.au - the federal government's data hub.
Freight Data Hub - various freight data including rail, road, port and air freight measures
Google Transit API - the official Google Transit API website, which provides specifications for exchanging both static and realtime public transit information, including information about stops, routes, schedule, service alerts, and other details.
Google GTFS Overview - the General Transit Feed Specification (GTFS) can be used to share static public transit data.
Google GTFS Realtime - the GTFS-realtime Specification is an extension to GTFS that can be used to share realtime public transit data.
Google GTFS Proto File - this file specifies the hierarchy of elements and their type definitions. Here is a link to the TfNSW Proto File which describes the tfnsw vehicle descriptor extension 1999 that includes aircond and wheelchair accessibility.
NSW Open Data Portal - the NSW government's data portal.
Stackexchange Open Data Community - get help and join in the discussion on Stackexchange's open data community website.
TPA - Transport Performance and Analytics (formally known as the Bureau of Transport Statistics) operates as a Centre of Excellence within the Planning and Programs Division of Transport for NSW. It provides objective and credible transport data, advice and analysis.
Transit Feeds - an extensive archive of public transit data for software developers, transit agencies and more. Browse and download official GTFS & GTFS-realtime feeds from around the world.