Just registered at force.com and I really have to say: easy going!
Purpose was to check out how easy it is to built own apps in the cloud and how to host own web sites.
A set of videos helps you out and provides helpful information.
I understood how to build own apps, although I faced some more complex processes to follow and data sheets to fill in.
How to build web sites, I did not discover yet. But, I’ll be sure to find the right path soon 😉
aViewOnIt 
Great intro….made me curious! However, do you need to have a clear idea in mind on what you want to do before you join or do the ideas first come once you are in?
both, you get inspired and you would have to know what type of app you wanna create. Otherwise, there is just to many things to do, before your app goes life.