My favourite app is probably 'Trains'. I think it's UK only, but I'm sure there are equivalents out there. It is very simple - it tell you departure and arrival times for trains from most (if not all) train station in the UK. It tells you routes, and whether train are cancelled or running late. The interface is so amazingly simple to use, it's never once crashed or let me down. Boring I know, but what can I say!