Your favorite pdfs?

I just got an iPad, which means that for the first time in my life it’s convenient for me to read long documents from the internet. I’ve often looked at things and thought, oh, if I ever have some capability to read that, I should. However, I haven’t made a list.

So. What documents in pdf form, or long websites, should I read now that I can? Any recommendations?

EDIT: Thanks for the advice. I’m particularly excited to read Godel, Escher, Bach. I’ve also downloaded the ePub of the Sequences, and I’m going to certainly look at Strategy of Conflict. Thank you very much for the links.