I don't know of anything Disney-specific (it might exist, but blank paper or a Word doc works just as well), but I use
Evernote for any vacation planning (and lots of work-related things).
I can use the online version from any computer, or the one on my desktop at my own computer. This syncs with my iphone (or any smartphone) as well.
You can make "notebooks"(folders) in there, and there are lots of extras Evernote offers, such as web clipping (if you see an article on DisneyFoodBlog that you want to clip and save to Evernote, you can do that with a click, for example). So I set mine up something like:
Reservations/Info - reservation codes/numbers, important phone numbers, addresses, etc)
Rides/Attractions - This is where I put our "MUST DOs", Fastpasses, and notes on these
Food - Meals/food I really wanted to try.
In each of these folders, I had a page for each of the parks (MK, EP, DHS, AK)....except the first, which was mostly accomodations and travel related. I'm sure some folks would want to organize it differently than I did.
OneNote by Microsoft is similar, and comes preloaded into a lot of PCs.
You can really make it as detailed as you want - or not. I'm not a commando planner, but I do think planning is half the fun. I like to keep notes on recommendations from the board or reviews or friends. But I also like to be able to access it at the parks. You can also share your notebooks/folders so other people can access on their smartphones as well.
I hope that makes sense!