WebCalTides is a free service that provides tides, currents and sunrise/sunset calendars for your favorite tide stations. Data is pulled from NOAA (US/etc) and DFO-CHS (Canada). Just search for a station, then click the webcal link to subscribe. Works on Apple iCal, Google Calendar and Outlook, maybe others.

Keyword or GPS: Units:

Written by Jordan Ritter, with contributions from Paul Schellenberg to support Canadian stations. Project source at GitHub.

Update 2/2024: GPS-based searching now supports degree formats (with both +/- and cardinal directions), in addition to decimal.
Update 1/2024: Calendars now generate 1 month behind + N months ahead (varies depending on limits imposed by NOAA vs. CHS). Every month, the calendar will slide forward by 1 month, so you should never run out of forecast.