We don't recommend you to incorporate your company before your have valided your product, and have traction. There are many startups that incorporate too early but realize their business is not sustainable. Therefore, this is really something you should do only when you are 100% sure your business is going to work out.
A good indication of this is when you have some paying customers, or when a bunch of users are signing up every day.
You can easily incorporate your company at these sites: http://www.mycorporation.com/
https://www.incorporate.com/
http://www.bizfilings.com/,
http://startupr.com/
clerky.com
If you want to know which type of company type you want to incorporate as, please see this article:
http://mashable.com/2012/02/17/small-business-incporporation/
First most people, deciding which type of incorporation you should choose is
