Have been using iOS4 for quite a while, and was eagerly waiting for iBooks, which will opens up the world of books in my palm.
Earlier rumor that iBooks will not be made available to iPhone 3G is now crushed, iBooks in here, is in my iPhone 3G NOW!!
the PDF Library, where my WWDC slides are kept that I can refer anytime.
PDF slide in action
The Project Gutenberg book, downloaded from iBooks Store