For
iphone I like Day Tides. No
internet access needed. It will give you the tides at any station in the world but just for that day. Tide Planner is the paid version and you can specify a different date. But you can of course reset the system date to the date in question and Day Tides will think it IS that date and give you the info. Cludgy but okay for a free app.
Also for iphone the rather expensive
iNavX, but only for U.S. coastal waters. Very good chart
navigation program. Only problem is you can't load
charts directly from your computer so if you have a big library of
charts already, you are still stuck with the US NOAA free charts and free charts from some other areas, unless you subscribe to their site. Still, excellent for US waters.
I just got my first Droid, a Galaxy Tab2 7" and I am liking it so far. I have Marine Navigator which can use charts from your PC. Works pretty good. Also
Google Earth. Great app but of course only when you have internet available.
I have a lot of my reference material on both devices. Bowditch, Coast Pilot, etc. Only truly essential stuff do I keep on my little
boat in hard copy.