I used a few apps over the 2 EC's I have done.
isailGPS; free app as a back up to GPS. Worked okay. A little basic but it can get you out of a jam. Can enter in waypoints and make route, tracks, etc. I bet Navionics is better but this one was free! (the irony of possibly having to rely on a free app isn't lost on me!) We used this app for a few minutes in Sarasota Bay when our Garmin had an "issue" for a few minutes and took a nap. For free I'd recommend it.
Tides/gulf of mexico; pretty good app. Has a google earth overlay, shows nearby tides. Has some pretty good features. Used it a lot in both races. Recommended
Florida Tide Times; pretty good. Used it a few times.
MyRadar; weather app, nice graphics. Pretty good for spotting the "black wall of death" before it hits. Has a few different screens for weather. Recommended
Windcompass; weather app, not that great. Basic and dull. Didn't use that much, probably better apps out there
weatherunderground; Forcasting and weather. Pretty good. I'd recomend it.
Marine Trafic; pretty good but only really useful for a few small portions of the start. Interestingly Per and I didn't use it at the '14 start when that ship came through. We went ahead of it but I was super nervous. If I was on the tiller I would probably have gone behind. We made it and there were others much closer than us. Fun app, recommended. I still use it all the time and I'm in VT. Just fun.
Google earth; Backup to a GPS. Can help out making sense of where you are.
Skype; Great for talking to the kids while we were racing. Used it a few times. Had a great
IHG; International Hotel Group, you never know where you might have to stop.
Another side topic here, what else did people use/load on their phones? I had a bunch of phone numbers preloaded. Hospitals, rent a car locations along the route, West Marine, Havanah Cafe, tow boat, hotels at the finish, checkpoint people, Chief, Paula, marinas, etc.