Once there was the free online tutorial, but before it was finished, the work that was done led to a book contract; so the author of the tutorial decided to write iText in Action. The book is the ultimate tutorial if you want to get started with iText; if you want to convince yourself, just register on the iText Software Corp site and you'll be able to download chapter 2 for free.
After the book, a wiki was started with some extra examples explaining new functionality added after the book was written (for instance: portable collections), but we definitely need a new tutorial to cover more recent features (for instance: separators). Most of the time, we have examples, but no real tutorial or article explaining what happens in the examples.
That's why a new series of tutorials is being written (starting in July 2009).
These tutorials won't be available for free. They may form the basis of a new book, or access to the tutorials may be available after payment of a small fee to 1T3XT BVBA. These tutorials are "under construction", there's nothing much to see for the moment, so please don't ask for a username/password yet.