Edison Media research has posted guide to covering Election Night, which includes the following handy listing of when polls close throughout the night and the corresponding electoral votes that will be decided at those times:
7:00 PM – 58 EVs
7:30 PM – 40 EVs
8:00 PM – 171 EVs
8:30 PM – 6 EVs
9:00 PM – 159 EVs
10:00 PM – 20 EVs
11:00 PM – 81 EVs
1:00 AM – 3 EVs
All times Eastern. Hat tip: The Corner
Update 11/2: For those coming from Edison Media Research, be sure to check out the TTLB Election Resource page, with links to a wide range of election-tracking resources which can be displayed as a sidebar in your Mozilla or IE browser.