I sometimes wonder how we managed before we had so much information and supports available via our phones and tablets.
I have used PredictWind for a long time now, great for planning and great to be able to monitor the weather systems from days to a week out and great to be able to compare the many forecast models. I have found in incredibly reliable. One point that is really useful is the gust Map, that generally makes you think again about certain plans and bays. The local knowledge with Historical Weather is also great for planning trips well in advance.
The app I use most for navigation and navigation planning is the Boating App from Navionics. Just great value for money and great to get the aerial photo of a bay to help familiarise in advance of arrival. However I also use this with Google Maps satellite view to help orientate myself on arrival.
As I have B&G instruments on board, I have started to utilise the B&G app more and love the fact that I can use my iPad to replicate my chart plotter anywhere on the boat.
More recently I have been relying on Windy for wind and wave patterns and its surprisingly accurate, I also found the Thunderstorms tracker very useful.
My newest and probably the most used app in the last few months of sailing is Navily. It's just a great community app detailing anchorages, and local amenities, and even found some local engineers for odd jobs. Also used it to get some great prices on marinas and was able to book online without hassle.
I do have AIS on board so get nearby ship info on the Instruments and mobile devices attached , but also like the simplicity if the MarineTraffic App to determine details of surrounding shipping.
So lots of apps and more becoming available all the time. Just hard to think back to the days of pilot books and charts (which I love and still carry on board).