Luggage and bags:
when going to Pnom Penh, dont bring hard-cased bags or mallets. Its stupid. Even if you're staying at Raffles Hotel! You are not in New York. Just bring a very big handy bag or 18-litter backpack used for camping or mountain climbing.
when roaming around, bring a handy-dandy backpack for where can put things you buy.
Clothing/Shoes/Weather Gear: wear light, cool clothing. Shorts for men, but not really for ladies unless you wouldn't mind the stares. Hiking shoes and sandals.Bring RAINCOAT! Or else you'll find yourself stuck in your hotel.
Toiletries and Medical Supplies: Paracetamol, Clyndamycin, Immodium
Photo Equipment: memory cards! I find it hard to find where to print digital pictures in Pnom Penh (august 2006) although I've seen 1 i forgot the street.
Miscellaneous: condoms. Lol
Pack a lot of Tshirts as its hot and humid all through the yeat. Even in December which is a much cooler time of the year I was sweating bullets and my shirt was drenched in sweat.
I did not find any insect or misquito problems, maybe december isn't too bad.
It is hot in Cambodia. When visiting Siem Reap, wear open, hiking shoes so you can visit as much as you can.
You will be tempted to buy a hat if you don't bring one with you. If you ride in motorcycles and you don't like to ruin your hairdo, wear, by all means, a hat.