I have a Nikon D40 (which I love!). i also take my distance lense and by the time we travel, I should have an extra flash. I also have an Olympus waterproof camera for the beach. On our last trip, I took my mini-dv recorder, but am experimenting with using the Olympus for video.
I'm thinking of getting an iphone in the near future, in which case I might (gasp) - only take the iphone and leave all the other gear at home. I hear from iphone lovers, that is all you need.