found here on the Maine Maritime Acadmey website, Captain G.A. Chase reports a rogue wave off Charleston, SC:
We were on the wing of the bridge, with a height of eye of 56 feet, and this wave broke over our heads. This shot was taken as we were diving down off the face of the second of a set of three waves, so the ship just kept falling into the trough, which just kept opening up under us. It bent the foremast (shown) back about 20 degrees, tore the foreword firefighting station (also shown) off the deck (rails, monitor, platform and all) and threw it against the face of the house. It also bent all the catwalks back severely. Later that night, about 1930, another wave hit the after house, hitting the stack and sending solid water down into the engine room through the forced draft blower intakes.
The conditions were not especially bad before this rogue wave hit, as Captain Chase puts it, "It was actually a nice day with light breezes and no significant sea. Only the very long swell, of about 15 feet high and probably 600 to 1000 feet long."
The lesson is that it is not necessary that the weather be awful for a unexpectedly large wave to appear at sea and cause serious damage.
Update: Interesting article on "freak waves" from the BBC here.
Update2: And some more "heavy weather" photos here, though to be fair, the weather was pretty bad generally in most of these.
Update3: More heavy weather - this time the "perfect storm" and the US Coast Guard is out trying to rescue people as seen at this site. In this photo, take look at the small Coast Guard boat enroute to help a yacht crew.
(Coast Guard photo by Chief Petty Officer Scott Vriesma.)
And you thought it was just a movie...