""The second new feature is that we've enabled 'wildcard' domains for App Engine apps serving off appspot.com. What this means is that you can now create multiple subdomains for your App Engine app, and have them all served by the same application. Thus, your users can access 'myapp.appspot.com', or 'developer.myapp.appspot.com', or 'news.myapp.appspot.com', with your app deciding how to handle each request. No setup is required to use the wildcard domains - simply configure your app to serve up requests to these subdomains however you wish. You can detect which domain a user requested by looking at the 'Host' header in the incoming request - for example, in Python's webapp framework you can access this with self.request.headers['Host'].""
AppEngine is pretty much awesome when you want to reduce web portal hosting costs. I am rewriting/augmenting a Rails web app in JRuby + Sinatra + DataMapper so it will run well on either Java AppEngine or one of my own servers using (C)Ruby. If my project gets a lot of users I would like to keep my costs down. (I usually deploy to Amazon AWS, but if you can live within the AppEngine restrictions, then AppEngine is even cheaper than Amazon.)
The ability of receiving email sounds good, but I usually only use this for new account verification - with AppEngine you can just use Google accounts.
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..)
There are still a few details, such as not being able to do https through your own domain (and apparently even for this new feature your app can only receive e-mail at your appspot domain) that may still make having a good appspot name important.
I guess if you had some clients to that app still out there (say, installed apps) somewhere, server gets deleted, but clients then try to connect to it - in the meantime someone has snapped up the name/URL and is collecting data from unsuspecting clients.
