This is a pretty exhaustive list: choose what you think you will need. Those items with a `*' are most important.
CAMPING/TRAVEL bowl * flashlight or headlamp matches mug * penknife * silica gel * sleeping bag * sleeping mat spoon * backpack, big or suitcase * backpack, small/daypack (sufficient for 3-day hike but _without_ camping equip/food) * luggage tags * padlock riverbag sunglasses * lightweight mosquito net CLOTHES bandana/handkerchief * boots * field pants * field shirts * field socks rain jacket * sandals sarong * shoes, hiking/running * shorts * sweater * swimming suit * T-shirts * towel * town/fancy pants * town/fancy shoes * town/fancy shirts * town socks * underwear * warm jacket * woolly hat FIELD GEAR * binos compass handlens * insect repellant leech socks * notebooks plastic bags, large and small permanent marker pens * sunhat umbrella * waterbottle MARINE antifog liquid * fins (with booties if needed) * mask * snorkel u/w camera housing underwater notebook or slate watch, diving weight belt * wetsuit (optional, but rec. for sun protection; lycra or 1-mm neoprene) MEDICAL/TOILETRIES anti-fungal cream * anti-itch cream antibiotic cream/powder antiperspirant * anti-malaria prophylaxis (malarone, doxycycline, daraprim, NOT meflaquine) anti-diarrhea * laxitive (our most commonly requested med!) * aspirin comb * soap ear plugs floss hand cleaner moleskin nail clipper psudafed razor scissors * sun cream (SPF 50) talc thermometer * toothbrush * toothpaste toilet paper tweezers * washbag * water purification tabs (vital) OFFICE/ID * ATM card * health insurance card * cash credit card dictionary field guides handphone charger * novels passport photo * passport and photocopies * pens, pencils, erasor handphone travellers checks * tickets * visa wallet TECHNOLOGY spare batteries blank CDs camera batteries * camera, digital * computer power computer video adapt * computer electric plug converters extra SIM card GPS headphones iPod/MP3 player spare SD cards SD to USB tripod