I've an apple iphone application out that stores data around the device. I wish to create an application with user accounts like Instagram, Path, Foursquare, Gowalla, etc.

Thus, I believe I will have to create an apple iphone client application, a MYSQL database, and PHP/Ruby on Rails for connecting the 2, together with the RestKit Framework for Objective-C.

What are the good books everyone would suggested for that after sales stuff? I'm confident with the iOS part, but don't have any history using the after sales/webserver side.

For learning PHP (I am presuming you are a new comer to PHP?) I suggest PHP Solutions by David Forces. For Ruby on Rails, take a look at Ruby on Rails 3 Tutorial by Michael Hartl.

Go ahead and take Rails for Zombies online tutorial.

Absolutely nothing to setup, just learn and code out of your browser.

If you want to review a brand new technology, I recommend purchasing a magazine, and not simply try to look for good quality lessons online. It will likely be money wisely spent esp. if you'd prefer your time and effort!

For Rails 3, among the best books is Agile Web Development with Rails (4th edition) - you can purchase a PDF at pragprog.com for $24, and it is ample to enable you to get began rapidly.