I used Northern Arizona Wind & Sun: Buy Solar Electric Panels
for my simple 40 watt panel with controller, which is more than adequate for my purposes. Solar panels are designed for outdoor use in exposed areas, so I am not sure exactly what the expensive "marine" designation buys ( no disrepect intended to MaineSail who is a true asset to this listserv). In any event, I can easily and inexpensively replace my panel if necessary. Last year, it survived quite a bit of abuse, including the derecho with 70 mph winds that hit me at Kiptopeake Beach.
I decided I wanted a solar set up after watching the following video (one of my favorite sailing videos) by Adrian Johnson, who won the 2010 Singlehanded Sailing Society's Transpac race in his Olson 30 "Idefix":
I later corresponded with Adrian Johnson and, just coincidentally, he bought his panels from the same outfit. Adrian Johnson later sailed his Olson 30 all the way across the Pacific to Austrailia or New Zealand, where he sold it, so the panels must be fairly rugged.