Bought a backpack today. It's brilliant: lots of pockets and straps, and has a detachable day pack. I've only two-thirds filled it, so there is lots of room to pack in souvenirs. Below is what I am taking. Total weight is a mere 22 pounds. I'll revisit this list when I return to see what I should have taken and didn't, or took and didn't need.
Bathroom
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Toothbrush
Toothpaste
Floss
Razor
Soap
Shampoo
Sunscreen
Medicines
Toilet Paper
Antiperspirant
Lip balm
Bug spray
Anti-itch balm
Diarrhoea pills
Advil
Few q-tips
Couple of bandages
1 Quick dry towel
1 hand towel
Clothes
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1 Pair of long pants with detachable legs
2 Shorts
Underwear
1 Long sleeve shirt
5 T-shirts
Sandal-type shoes
1 Bathing suit
Waterproof poncho
Hat
Gear
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Sun glasses
Camera
MP3 player
Watch with alarm
2 Locks
Keychain calculator
Money belt
Swiss army knife
Large ziploc bags
Travel book
Reading book
Earplugs
Nail clippers
Note book and pens
Backpack with day pack
Water bottle
Memory stick
Other
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Medical insurance
Passport
Credit cards and ATM card
Notable exclusions: sweater and coat (too warm), socks (who needs socks?), shaving cream (soap will do), hair spray / gel (yeah, right)