69. In a shipyard, on the deck of a half buit ship, or jumping from hull-thingy to hull-thingy (the big curved wooden dealies that comprise the frame of a ships hull)
That's "ribs" and "deck beams" that you're thinking of...
Undead seagulls...I like it. They don't snatch your lunch out of your hand, they snatch your hand off of your arm

Fear the seagulls!
75) In a mine - a mine that's falling in around the player's ears.
What Makes it Memorable? Every round there is a 50% chance of an area of ceiling 30' by 30' falling on the characters. Reflex save DC 15 or be squished - while fighting assorted foes.
76) In a room for of machinery - giant, rotating gears, cogs, chains, pistons, etc.
What Makes it Memorable? Reflex save DC15 every round or be caught and dragged into the machinery. PCs can Bull-rush enemies into the machinery, and be bull-rushed themselves.
77) In free-fall...and the suicidal foes are all encased in antimagic shells.
What Makes it Memorable? The foes will try to grapple the PCs and drag them down (make the foes some kind of monster with ridiculous bonuses to grapple checks, if feeling sadistic).
Can't think of any more right now...