On our honeymoon in Lanzarote all I had was my Panasonic Lumix DMC-FZ5, 2 1GB SD cards, a spare battery and charger.
Little did I know that I would wish for a wide angle lens when we visited Cuevo De Los Verde (along with an English gentleman who missed his tripod too) but I still got some stunning photos of that cave. Everyone started copying me after a short while by disabling the flash and shooting long exposure images while balancing their cameras on suitable rocks. The lighting in that cave is drowned out by a flash but with a little care I captured a few beautiful images. Unfortunately my camera case is scratched badly by the volcanic rock so it’s probably a good thing I didn’t have the 20D! I’m taking a bean bag with me next time!
I digress, here are some suggestions for what you should take with you on holidays. Take a look at the rest of Digital Photography School, it’s a fountain of information and I’d be here all day linking to the great articles there!