Note: This list is based on your planning to do laundry at in the middle of the trip.

GIRLS: Long skirt for holy sites (pants are acceptable)
BOYS: Several Kippot, Tallit Tefillin
ALL: 2 Long-sleeved shirts (Winter)
12 Short-sleeved shirts
1 Sweater/sweatshirt
3 Jeans/Khakis
1 Pants (athletic-type for outdoor activities)
1 Outfit that can get dirty (for archaeological dig)
1Bathing Suit
2 Shorts
1Nice outfit for Shabbat and going out (not too expensive and fancy. Girls - dress or skirt and blouse, Boys - white shirt and trousers - tie and jacket NOT necessary!!)
12 Socks
12 Underwear
1Comfortable walking shoes
1 Water sandals (shoes you don't mind getting wet) - not flip-flops (must be shoe with strap around back of ankle, e.g. Tevas)
1 Sandals or Shabbat shoes
1 Bath towel
1 Rain Jacket /poncho
Hat (MANDATORY)
Alarm clock
Electrical current converter and plug adapter (for hair dryer, shaver, etc.) (Israel runs on 220 currency, and the plugs are different. It is hard to find the right plug adaptors in the U.S. sometimes, so do not rely on hairdryers, ets.)
1 Sunglasses (INEXPENSIVE PAIR)
Glasses/contact lenses
Backpack and/or fanny pack

Small duffel bag (packed empty to carry home gifts/souvenirs acquired)
Camera and film (better to bring than buy in Israel)
Toiletries/Personal items - (soap, soap dish, shampoo, toothbrush, toothpaste, comb, brush, deodorant insect repellant, sunscreen, extra glasses or contacts if you wear them, feminine hygiene products)
Laundry bag
Flashlight
Wallet