I see there are now a few books in Oâ€™Reillyâ€™s OFPS â€œexperimentâ€â€¦.
- Programming Scala
- Rails 3 in a Nutshell
- Using SQLite
I like this open, agile approach to writing a book and hope that it is a success (in commercial terms as well as for developers who get to read the content as it written)