Citymapper - The ultimate transport app - iPhone / Android / Web.
Magpie Maps - Advanced UK public transport isochrone/reachability maps
Embark - A public transport app that works everywhere
Omio - GoEuro's new app, book travel transport in Europe 🇪🇺
Tickey - Buy tickets for public transport with your smartphone
Moovit - For people that use public trasnportation a lot, or who rarely use it but need to on occasion, it can be difficult at times to figure out where you need to be to get where you need to go. Read more about Moovit.