Amazon

• Get to own a project independently and drive it to completion.
• Intern projects are valued; mine and many others made it to production.
• Strong mentoring is provided (you are given one mentor for the summer with whom you work closely).
• Experience with the Amazon development process (even though you are not partaking in your team's Agile activities, you can sit in on those meetings and participate).
• An offer for post-graduation was immediately extended.

You need a deliverable at the end. Even if your project is going really well, if you don't have anything to demo at the end of it, it's almost like doing nothing.

The last 1-2 weeks are mostly demos.

Your project is (usually) isolated from what the rest of the team is working on.