This is my fourth baby.

I have 2 daughters and a son, but this is the baby that makes everything possible.

iPhone

This is my iPhone, but a refurb'd Touch will work just as well (sorry, I'm not familiar with a non-Mac product, like a Droid device, to recommend - if you are, please mention it in the comments.) You can get a refurb iPod Touch at the Apple store for $149. For the Touch, you can do anything you can with the phone (except calling) with a wi-fi connection. As most schools that have Wi-Fi will not give out the WEP key (sucks when you've saved links and realize you can't access them at an ARD) - make sure to save your documents by syncing your Awesome-Notes with google docs (where you have helpfully copy/pasted the relevant information).

I use the included Calendar (very functional!) to keep track of our therapy appointments, IEP and ARD meetings, Big Sister outings, doctor appointments, and medication refill reminders. The included note system is limited, however, and I prefer the app "Awesome Notes". I have my gmail synced to the phone so that I am ding'd every time I get an email (often from a teacher, doctor, or therapist); and I have my notes as above synced to google docs. It is amazing how much information you can have on you that fits in your pocket.
The Facebook app allows me to check for notifications to posts or questions I've made to various networking groups or people.

What do you use to keep yourself organized in the overwhelming scheduling of caring for a special needs child?