I have approximately two-thirds of the planning for my NaNoWriMo project done in Scrivener, which I will use for the actual writing. I have all major character and place sketches, complete with tons of images, my chapters set up, and notes for each scene within most of the chapters. This will form my outline.
The logic behind this is: if I have a block/panic attack/whatever on November 1st, it won’t really matter. I will know what I need to write, and can just grab a scene and write it out of sequence, without the huge and daunting task of just starting at the beginning and continuing on from there. I understand there are a lot of “pantsers” who prefer to not work with an outline, or even more than just a very general idea of what they will be writing, but I can’t imagine doing that.