I use iSailor on my Iphone4, and love it. It is no substitute for paper charts, but is very useful for blowing up small harbor entrances, if the paper charts you have on hand don't quite give you the detail you desire. It is also awesome for trip planning, estimating cruise
time, distance, etc. It would be much better used on an Ipad
, but since I don't have one..
Best of all, the app is free, full charts for a large area are around $10 once you download and try it out. Once the charts are downloaded, you don't need a phone connection - as most of the places I cruise
don't have a cell signal anyway - it simply relies on the GPS chip.
For paper charts, I LOVE "Booklet Charts" from NOAA, they are free, and sized to print at home on normal paper. Just print, 3-hole punch, and put in a binder. On my small boat, they work better than full sized charts, as I don't have a chart table (Albin Vega)