There’s a lot to watch for tonight, and for a less wonky take, check out Josh Marshall here.
First, the short version, if you don’t want all the details. The first key is Virginia at 7 PM. If Obama takes Virginia, where he’s ahead, he’ll almost certainly take Pennsylvania (at 8 PM) too. And that will pretty much be it for McCain. Between 6PM and 8 PM there are five other states: Indiana, Florida, Ohio, Missouri, North Carolina. These are all basically toss-ups with a few slight leads for Obama. If McCain is losing in any of them, he’s probably done.
More details in the link.