If I want to get started with App Engine but I have no experience, not with online apps nor with Python but I really want to learn, where would you guys suggest I start?
Sanderson's "Programming Google App Engine" book is now available through OReilly's Rough Cuts.
The MEAP version of "Google App Engine in Action" is in flux because the previous authors had another commitment. It turned into a positive, though, because Nick Johnson became an author. He's on the AE Team and has contributed a lot to the knowledge base. Check out his blog at http://blog.notdot.net/
I'd recommend sticking with the basic webapp handlers in python and not trying to learn django, etc.
Just write a simple app that you think would be fun... maybe a blog app, or a simple forum, etc.
Python is pretty easy and the python libs have very easy to understand source (and decent documentation) in case you get confused.
If you really have zero experience with web apps, you might first want to play around with Sinatra a bit on your laptop, but the webapp framework on app engine is actually fairly similar to sinatra, so either one would be fine.
I would start with the tutorial http://code.google.com/appengine/docs/python/gettingstarted/. They also have a Java API if that is more to your liking. See if you can follow and understand the tutorial and fill in any gaps where you seem to be lacking in knowledge or understanding with other sources. If you know any programming language I think the Python is relatively easy to follow.
Since AppEngine runs Java, that means it can run JRuby, which also means it can run Rails. Use it if you like. There are a couple of special considerations when using Rails on App Engine, although I am not familiar with them. Finally, you should remember that you're stuck with their datastore, so you can't use ActiveRecord (at least as far as I know, there may be a gem that lets you)
Python should be easier to pick up. I knew very little Python before using GAE, looking back there was hardly a learning curve. It's almost like writing pseudo-code. (Though somehow not as fun to code as Ruby, for me..)
http://billkatz.com/2009/1/Upcoming-App-Engine-Books
Sanderson's "Programming Google App Engine" book is now available through OReilly's Rough Cuts.
The MEAP version of "Google App Engine in Action" is in flux because the previous authors had another commitment. It turned into a positive, though, because Nick Johnson became an author. He's on the AE Team and has contributed a lot to the knowledge base. Check out his blog at http://blog.notdot.net/
Other web links you may find educational:
http://blog.appenginefan.com
http://appengine-cookbook.appspot.com/
http://gae4dummies.appspot.com/
And if you are in the SF Bay Area, go to the local meetups:
http://meetup.com/appengine
Even if you're not local, check out the group because we just started posting videos of the meetup. (See message board for links.)