One of the fun parts of a cruise is coming into your room every night and being greeted by a silly bit of "towel origami". Like this:
Image Courtesy of: Squidoo
Imagine this cute towel animal greeting each of your out-of-town guests as they enter their hotel rooms! It's an imaginative (and useable) alternative to the traditional guest basket. Do a monkey wearing a pair of sunglasses or create a bear clutching a bottle of water. Seriously, your guests will totally be talking about this! Be sure to include a note from the two of you so that guests know that you're the one that did this little treat (and not the hotel's staff).
The best part of this idea is that the origami animals are totally free. Simply explain your ideas to the hotel staff (you will probably need the approval of the hotel manager) and request a stack of hotel towels and a spare room. Print the directions, make copies for friends, and start DIYing.