Navionics — online charts. Get the US/Canada combo if there’s any chance we’d be boating in Canada since it’s not possible to just add-on Canada, you have to repurchase the whole bundle. Fee-based.
What knot to do — knot instruction from Columbia Sportswear. Categorized by sport, so there’s a sailing category. The reef knot is in camping, fyi. Free app.
My Radar Pro from NOAA — great for locating storms; can set alerts for if there is precipitation or lightning within a certain radius. Fee-based to get the pro version.