In addition to the most popular ones that have already been mentioned (Navionics, Tides, Buoys,etc), I have one called Peakfinder, which is fun to have here in the PNW where there are always mountains in the distance that need identifying. I also have one called Nav Lights which gives all the lighting configurations. And as someone else mentioned, Grog's Knots.
SV Laurie Anne
1988 Brewer 40 Pilothouse