Originally Posted by CKDGM

I use Google Maps for route planning, and Transit App for live bus/train times. Transit App is particularly nice IMO because it works in many, many cities around the world so you don't have to have a phone full of city-specific apps.

Originally Posted by NYCRachel

MTA finally has their own standalone bus time app (it used to be just mobile web).

Google Maps, NYC Bus app and Exit Strategy are my go-to's (the last is unnecessary for tourists though).