Apple added some of their on-line books to the iBooks store for off-line reading on your iPad (or iPhone, though I double people will use that for readong).
Since you can only get to those from your iPad/iPhone iBook app, I included google search links for the online versions:
- Cocoa Fundamentals Guide,
- The Objective-C Programming Language,
- iOS Application Programming Guide,
- Object Oriented Programming With Objective-C,
- iOS Technology Overview,
- iOS Human Interface Guideline
Note that iOS Human Interface Guidelines is not availeble outside the USA iBook store.
But it is almost as easy to read your PDFs through the DropBox iPad app (it even links to iBooks if you want to!).
Sharing your PDFs using DropBox has the added benefit that you can have the PDF both on your development machine and your iPad for reference.
–jeroen
via Apple Publishes Six Free Electronic Books for Developers | Cult of Mac.