I'm using OpenOffice Calc (an Excel clone) to plan my daily word-count goals and record my progress, and it'll automatically adjust the word-count goals for the following days based on that.
As for planning the stories themselves, I'm not, mostly because I'm using this year's NaNo to try to make progress on some long-in-progress stories/series. Yeah, I'm gonna be writing bits of multiple stories per day. Some are stories that I'm already writing and know where I'm going. Others are new stories, some of which have a short summary that I've written down, others of which I come up with as I go along.
I plan to tackle the following:
*story #03 in my "Betty and Cheryl" Archie fanfic series (I gotta spend the rest of today getting #02 done!)
*finish story #05 of "Vampire Killer" and write story #06
*story #05 of "Blackjack Jill"
*finish "I Can Kill You With My Brain", the next entry in my "Revelatio Dearum" metaseries
*finish the first story in my "Vanity City" series (futuristic cyberpunk tough cop series)
*finish "The Age of Ascension", the first story in my pseudomedieval fantasy metaseries
*finish story #01 of "Daughters of the Moon", my MG magical-girl series
Based on my word-count goals for each of these, I've estimated, to do all of them, I'd be writing 233 extra words per day above the daily requirement (1667) to reach the 50,000 goal, so I have a bit of leeway and can leave some things unfinished at the end of November, but I'd like to knock out the short stories at least. Five of the seven projects require a daily goal of 200 words or less.
Optionally, I could also work on "Our Lady of the Sea and the Moon", my Wicca spiritual novel. I'm also starting up a Sailor Moon fanfic series and could make some progress on that. Writing those would decrease the average daily word counts for my other projects.
My plan is to copy-and-paste all of my daily progress into one file for daily submission to NaNo.