Haaretz: She's very religious! She's rural! She's folksy! She's not an intellectual! She drops her "gs" and says "you betcha"!
Interestingly, the converse of the negative stereotype of the urban, slick, militantly secular, fast-talking Jewish intellectual that used to circulate widely in rural America. The rural folks seem have mostly gotten over it, and the Jewish urbanites (or at least the ones who aren't religious themselves) are now probably more prejudiced against them then vice-versa.
To clarify, there's nothing wrong about disliking Sarah Palin because you dislike her ideology, or criticizing her because you think she's unqualified to be president. (I presently share the latter sentiment, though I think Palin has real potential.) But to especially dislike her because she has a different religious and cultural background, while a not uncommon human phenomenon, smacks of the sort of prejudice American Jews have been fighting against for decades (and not just vis a vis Jews).
It's once again worth pointing out that none of the Jewish organizations who (properly) spoke out against anti-Obama emails based on prejudice against his part-Muslim background have said a word about Palin.
UPDATE: Some commenters are ably defending Palin's critics. But as a thought experiment, if it were a Jewish woman named Sarah Palinsky from New York running for vice-president on the Democratic ticket, and a Christian magazine had a story about how rural evangelical Christians women have a visceral near-hatred for her, not just because she's liberal, but because she's secular and has strange views on god, a "slick talker with a New York accent," too much of a cosmpolitan intellectual, and someone they see as a very real threat to everything they hold dear, I'm guessing the same commenters wouldn't be nearly as charitable.
And, of course, the prejudices exhibited against Palin's background are common among secular liberal urbanites of all religions. But you would think Jews, subject to so many unfair stereotypes themselves, might be more self-aware about such things then most.