just bought a small, zippered bag w/ elastic straps for our perscription meds-seems alot better than having to rummage through the room safe for the right bottle.
ditto on the bubble wrap-i just buy a couple of rolls and pack them w/some sturdy tape.
laundry tabs-the boxes come w/prewrapped packages of the tabs (less messy than a ziplock bag that breaks open mid trip!
double ditto on the over the door shoe holder-done this on both cruises as well as hotel vacations-saves so much time not to mention counter space.
labels preaddressed for mailing postcards (don't have to bring along my address book)-works esp. well for the kids.
inflatable "water wings" for the little ones-most liners don't carry due to liability issues.
I am considering investing in a small portable dvd player for next trip-I can use a cd carrier for the dvd's & this could provide some quiet entertainment for kids.
sarong-use it as a skirt, bathing suit cover, shawl....