The Excel file below allows users to play with the 2000, 2010, and their own population estimates to see how it affects the apportionment of seats for the US House of Representatives. Apportionment also influences the presidential Electoral College vote count for each state. To get the number of Electoral College votes for a state take the number of U.S. House seats and add two (recall that DC, which is not in the file as it has no seats in the US Congress, is given three Electoral College votes). Some explanation of the apportionment process and how to use this Excel file is on the first tab in the file.
Note: if you see any errors, or have useful comments, you can contact me at douglasrhess [at] gmail. Do NOT leave comments on this blog as I will not see them (we haven't updated this blog in a while).