ePub files

Tip:
If you drag en ePub file into the iTunes library window, and "books" is synced to the iPad, the book will automatically turn up in Apple's iBooks app, an app I like.

This can be used with those ebooks you can buy in epub format, for example from O'Reilly. And it can be used with those files that calibre collects from news sites, magazine sites, etc. They work perfectly in iBooks and look great.
(I'm told by the founder of calibre that they are working on a way to automatize this process.)

Note: "ePub" is a book/text file format, like MP3 is a music file format, or JPG is a picture file format. It is considered by many to be the Standard format for ebooks, and Apple chose it for iBooks, but irritatingly Sony and Amazon chose other formats for their ebook readers (the Sony Reader and the Kindle). This was spoken about today in a large book publishers' conference as one of the main things holding back the ebook publishing industry.