Things You Should DEFINITELY Bring:
-Modest clothing! (for all seasons) (And shorts to wear under your skirt--once you leave Meah She'arim, you can just whip that skirt off and be cool again!)
-Comfortable shoes are a must, especially for Jerusalem. I recommend padded sneakers.
-Bring enough toiletries, especially make-up--make-up is about 3X more expensive here in Israel!
-Bug spray and sunscreen!
-A Lonely Planet.
-A driver's license for renting a car, and extra passport copies.
Things You can buy without too much expense:
-Buy towels and sheets here, because they take up so much room.
-"Hippie"-ish clothes.
-Judaica.
-Flip-flops (I love the Haviannas with Israeli flags--thanks Sarah!)