Besides actually getting out to vote next month, being REGISTERED to vote is the next most important thing we need to do.  

This site has a very detailed look at each state's requirements, but here's a quick look at the deadlines for registering:

Alabama     Fri, Oct. 24
Alaska     Sun, Oct. 5 (postmark by Sat, Oct. 4)
Arizona     Mon, Oct. 6
Arkansas     Mon, Oct. 6
California     Mon, Oct. 20
Colorado     Mon, Oct. 6
Connecticut     Tues, Oct. 21
Delaware     Sat, Oct. 11
District of Columbia     Mon, Oct. 6
Florida     Mon, Oct. 6

Georgia     Mon, Oct. 6
Hawaii     Mon, Oct. 6
Idaho     Register at Polls
Illinois     Tues, Oct. 7
Indiana     Mon, Oct. 6
Iowa     Fri, Oct. 24 (or on Election Day at polling place)
Kansas     Mon, Oct. 20
Kentucky     Mon, Oct. 6
Louisiana     Mon, Oct. 6
Maine     Tue, Oct. 21 (or on Election Day at polling place)
Maryland     Tue, Oct. 14
Massachusetts     Wed, Oct. 15
Michigan     Mon, Oct. 6
Minnesota     Same Day Registration at polling place
Mississippi     Mon, Oct. 6
Missouri     Wed, Oct. 8
Montana     Mon, Oct. 6 (or same day at elections office)
Nebraska     Fri, Oct. 24 (mail by Fri, Oct. 17)
Nevada     Tue, Oct. 4 (or in person until Oct. 14)
New Hampshire     Same Day
New Jersey     Tues, Oct. 14
New Mexico     Tues, Oct. 7
New York     Fri, Oct. 10
North Carolina     Fri, Oct. 10
North Dakota     N/A
Ohio     Mon, Oct. 6
Oklahoma     Fri, Oct. 10
Oregon     Tue, Oct. 14
Pennsylvania     Mon, Oct. 6
Rhode Island     Sat, Oct. 4
South Carolina     Sat, Oct. 4
South Dakota     Mon, Oct. 20
Tennessee     Mon, Oct. 6
Texas     Mon, Oct. 6
Utah     Mon, Oct. 6 or in person Tue, Oct. 28
Vermont     Wed, Oct. 29
Virginia     Mon, Oct. 6
Washington     Sat, Oct. 4 (or until Mon, Oct. 20 in person)
West Virginia     Wed, Oct. 15
Wisconsin     Wed, Oct. 15 (or on Election Day at polling place)
Wyoming     Can register at polls