Stuff to bring on your sailing trip
(this may grow, so check it one more time when you pack)

1. Bathing suit
2. Camera (with a car charger or batteries), waterproof cameras are best, otherwise bring a dry bag or something waterproof to store it in when not in use.
3. Snorkel gear if you have room
4. Sunglasses/glasses with a lanyard - OR - spare pairs of sunglasses/glasses
5. Sunblock - this is important - also a shady hat is nice to have
6. Shoes with non-marking soles for use on the boat
7. Walking shoes or hiking sandals for trips ashore
8. Shorts/underwear/socks/t-shirts/shirts/pants/belt/etc - whatever clothing you usually bring on a trip. Pack light for warm weather, layers are better than a single warm garment. Breathable/hiking stuff is nice but not mandatory, and try to stick with light colors (white is best) for anything in the tropics. One warm garment (fleece or hoodie) is probably enough if we're south.
9. Prescription medication - if you take ANY medication bring enough for at least twice the planned trip length, as it may not be possible to refill
10. An iPod is nice to have, and we can hook it to the boat stereo if everyone likes your music.
11. Any and all personal toiletries you need for at least the length of the trip. For what it's worth, the Dr Bronners soap with all the crazy ranting on the label is the best for salt water, sometimes if we're short on water it's nice to take a swim and wash up, then rinse off with fresh water aboard.
12. Log book if you're doing ASA program
13. Reading material - a Kindle or Nook is fine but make sure you have somewhere waterproof to store it.
14. Passport! this is very important, double check it's in your bag :) Needs to have blank pages and at least 6 months of time left before it expires
15. Some spending cash - it can be difficult to get money out of a bank in some countries once you leave the airport, make sure you have enough for yourself playing ashore or emergencies, enough to pitch in for food, and if you're helping with fuel/immigration.
16. Harness and tether if you own one, otherwise we have some on the boat
17. Foul weather gear - I use the West Marine brand Third Reef line, but anything that will keep you really dry in a heavy downpour or a wave splashing you. Good to have the bibs (pants) as well as jacket.
18. Snowboarding pants will work kind of if you already own them and you're on a budget.
19. Car chargers (12V) or lots of batteries for all electronic devices
20. Flashlight/headlamp with a red light is great for night watches
21. Clasp knife (OK) or rigging knife with spike (better) or Leatherman or similar multitool (best)
22. Nalgene bottle or other water bottle

Try to pack light in soft bags as we have no space to store hard luggage. One duffel is ideal, but not a major issue if you need more. If you have extra space and feel like contributing something fun to share with the crew, some items past crew have brought are a favorite hot sauce, good coffee, chocolate, a travel version of your favorite board game, soccer balls (deflated!) to donate to kids in out-of-the-way ports, or a small musical instrument.