It is indeed going to be on tomorrow as well (although the Wednesday airing will only be a half hour, compared to the hour long airing tonight).
BTW, DC area viewers will have to wait Saturday afternoon to watch the hour-long version, as it's been pre-emptied for coverage on the upcoming Virginia elections.
I love this Halloween classic, I love almost all the Peanuts stuff from their holiday boxed set minus the New Years special and that second god awful Christmas special, but this Halloween gem is one of the best Peanuts episodes of them all. Linus' refusal to believe that the great pumpkin does not exist is so funny and Sally's response to him when the pumpkin does not arrive makes me laugh year after year, this special is just simply amazing.
I hope kids of today's generation are enjoying it as much as I did at their age (and still do).