When you leave Facebook, you have the option of exporting your data. This is a token gesture, because the real value of the data you entered over the years cannot be exported. For example, you don't get your friends' email addresses or any other way to communicate with them. If you've come to rely on your Facebook connections as the only way to contact someone, you'll need to do extra work. Here's what I did.
First, post a message on your wall like this:
I'm leaving Facebook in a week, but I'd love to keep in touch. Send me an email or a text message! email@example.com (123) 456-7890
Now go through your friends, one by one. Have your non-Facebook address book open side by side. Make sure your address book is up to date. Don't be afraid to delete entries for people you never communicate with. Chances are you have outdated info, and it's not hard to track people down these days. Many of your Facebook friends are people you can contact some other way, so don't worry about them. Many are friends-of-friends that you probably don't really need to contact. If you ever do, you can ask your mutual friend for their info. Same with relatives; If you need their phone number, you can probably just ask your mom. The other 50%? Who cares. I was left with a dozen people to whom Facebook was my only connection. I sent each of them a personal message to get their email and phone, and to let them know I'd be off Facebook soon.
Click through all the photos that other people have tagged you in, because you don't get those in the export. Right click on each one and download it to your computer. By using keyboard shortcuts and the mouse together in a percussive rhythm, you can go through all of these pretty quickly and systematically.
It's not easy to actually delete your account. Every deleter I know has stories of the byzantine steps that were required, and even then some have doubt that the account was actually removed forever. At the time of this writing, this is the deletion form you need to use, but it's worth search around the net for current anecdotes.
And so for posterity, here is my exported Facebook profile in all of it's inanity.