Navionics Boating HD
Radar Express
Marine Weather by Accuweather
Live Weather
NOAA Weather
Anchor Lite
BoatUS
I've tried various other apps, but so far those are the ones that have stuck with me. I also have a 10" Android tablet, I have Navionics installed on that as well, and use it to supplement my on board GPS plotter. I use the tablet mostly for navigation / route planning, while I use the on board GPS to monitor depths.
-Kevin