Tripview gives you an easy way to work out if you should run to the train station to get that train, or simply wait in the pub another fifteen minutes.
It's not an exaggeration to say that I use Tripview every single day. The premise is pretty simple; it gives you the Sydney timetable for trains, buses and ferries, and lets you select journeys and (with the paid version) save them for later usage, so your most common trips are but a click or two away.
Timetables are updated regularly, and trackwork is noted onscreen so it's easy to estimate quite how late you're likely to be. Yes, it only covers Sydney, and sure, it sometimes misses trains -- but that's probably more Cityrail's fault than Tripview's. [Tripview]