I have recently finished learning PHP and after getting familiar with AJAX and building a couple web aplications I decided I would like to learn to work with the diferent API's from websites like facebook, twitter, google+, google maps, youtube and amazon.
I found this book on amazon.com: Pro Web 2.0 Mashups witch seems to cover Google Maps, Amazon, RSS feeds and some others, but it is from 2008 and I tend to think that books that are older than 2 years from the current date are a little old. If that is not true please let me know. Although it really seems that it could be helpful I would like to learn them in the order I mentioned.
Can anyone recommend any books that cover the API's I mentioned?
Why don't you just go to the developer section of each one of those companies. You will find the most recent information about those APIs there with even some sample code in the most popular programming languages.