This can’t be stressed enough. Red states are going to try their damndest to keep those they feel may vote Dem from voting for any number of bullshit reasons.
The Obama/Biden campaign has a website where you can go to quickly register or check whether you are. Just takes a few minutes:
The McCain campaign? Well, I’m hearing on radio shows that registered Democratic voters are receiving absentee ballots by email courtesy of the McCain campaign and that many of them have PO Boxes as sending addresses and/or wrong addresses printed on them.
If I were you, I would not trust them at all.