5 T-shirts.
5 pairs of socks.
5 pairs boxers/briefs.
3 shirts.
2 pairs shorts.
2 pairs trousers.
1 suit.
2 pairs shoes.
1 pair flip-flops.
Washbag, with shaving kit, toothbrush/paste, shower gel, shampoo/conditioner, deodorant/body spray, floss.
Small first-aid kit.
Sun-block & after-sun.
Travel adaptor for plugs/USB.
Noise-cancelling headphones with airline adaptor.
iPhone, possibly a netbook as well, depending on destination.
Camera, lenses, basic cleaning kit, spare battery and SD cards.
Chargers.
A tome of a book.
Sketchbook and small drawing kit.
Beach-towel, unless staying at an hotel where they'll be provided.
Lightweight soft-shell jacket, just in case.
Travel wallet with documentation, passports (plus photocopies), tickets, local currency plus US$ if in Asia or Africa, AMEX cheques or card.
I think that's about it.