areo weather- gives you all the TAFS for all the airports you set. very good.
FlightCom UK- quic kreferance list of radio frequencies. however said to have a few mistakes.
xWind- quick cross wind calculations
myConcert- good for many things other that flying but i use it for distance calculations as well as speed.
AirTycoon- nothing to do with helping you fly yourself but fantastic game to play and great fun for many hours. infact its the ONLY app i have payed for so far on my phone. everything else including the ones above are free.