Some of this is going to be straight out of my ass.
Some of this is going to be based on actual demographics, but I'm going to do piss poor research.
Most of this would be exactly what I would have said if "random anti-abortion evangelical big game hunting extremist" was picked for vice president.
And we'll start with the easy one:
AK: Alaska was polling close. It is now completely out of reach for Obama. The Palin pick is also bad news for down ticket races, as Alaska Republicans rally behind their corrupt politicians and libertarian welfare state in the glare of national scrutiny
OH: Palin is a net neutral here. Yes, SE Ohio is full of rural evangelicals. And yes, high turnout among them helped Bush carry the state. However, Ohio is NOT a largely rural state, it's full of cities and suburbs. As an aside, the Obama campaign needs to run the $50 an hour picking lettuce spiel in an ad here again and again and again.
MI: Another net neutral. She has appeal to hunters but the Republicans need to do well in the Detroit suburbs, I doubt she helps much here. Another lettuce ad state.
MT: Not highly evangelical, but chock full of people who love shooting large animals. Now out of reach for Obama. Probably always was.
ND: Also now probably out of reach for Obama. Probably always was.
NC: Palin helps McCain here. A lot of Southern Baptists/Evangelicals. It might be out of reach for Obama -- or at least off the list of swing states. Before Palin, a Southern strategy was imaginable where NC would be key. Now, it's highly unlikely it's not a route if Obama wins. qmastertoo is more sanguine about the prospects in NC than I am. He may be right that she doesn't play as well as I think she does. But the chances of Kerry+VA+NC winning the day for Obama in a squeaker still seems less likely than it was before to me.
CO: I'd expect her to be a bit of a help here, as the evangelical movement is strong here. There is, however, also a decent amount of Obama base voters here, and their increased motivation due to the Palin pick could be good for him.
VA: An EXTREMELY mixed results state. Palin is a big winner among downstate white voters. She should be a big loser among the educated, wealthy, suburban Northern Virginians. Keep in mind that most of the population of Northern Virginia is more qualified to be veep than she is, and that doesn't sit well. It's a place full of people who were a little worried about Obama's lack of experience but Biden and Palin as the picks help Obama a lot.
NH: Palin cedes the state to Obama. No real evangelicals to speak of. Chock full of Catholics with a few Mainline Protestants. Lots of voters who used to believe McCain is a moderate and now realize he isn't.
FL: Another mixed results state. Helps McCain with turnout in the North. If you know any Jews in South Florida, though, three words: Jews for Jesus. Anyone who was worried about Wright is going to just LOOOVVVVE Palin's pastors.
PA: Helps McCain in most of the T. Helps Obama in the Philly burbs. I actually think picking Palin is an overall negative for McCain here. His only shot was not just running up the totals in rural PA, but doing well in the burbs. Which are full of educated Jews, Catholics and Mainline Protestants who don't hunt.
MO: Helps McCain A LOT. Yes, based on demographics, you'd think I'd be saying it will be mixed results. But a large chunk of the state makes SE Ohio and the T look like cosmopolitan worldbeaters. Or, Palin might be mixed results in the St. L and KC burbs. And Obama was already doing well in the cities. But Palin is going to be huge everywhere else. Might be off the table, at least as a swing. TomP and others point out that a lot of the state is NOT that evangelical and that it shouldn't be written off. (Along with some other good points.)
NV: Mixed results. Palin probably plays well outside of the cities and suburbs, but is mixed in Clark and Washoe. Unfortunately for McCain, almost everyone lives in Clark or Washoe. How many Jews live here? I've seen figures ranging from one 1% to 4%. Given that Palin may well be moving close to 25 points to Obama (I'd say from 60 to 85. No joke.), if it's 4% Jewish, the Palin pick is a gain of a full point for Obama (and a net of two).
NM: Not much of an impact, negative or positive. Sure, some I think the polls showing McCain gaining here are weird and are showing the race a lot closer among Hispanics than it should be. Maybe there's a successful McCain Spanish language ad campaign I don't know about. Seems like polls should return to where they were, a slight Obama lead.
Any states I missed? Any disagreements? I'll likely edit this if someone makes a good point. (And give props.)