I stumbled across this blog post by Tomasz Tunguz of Redpoint that mentioned a really interesting site - pretty self-explanatory - UserOnboarding.

The site details critical aspects that impact the user experience at the initial stages of learning about a site's product or service. Lots to walk through here to understand what's important and why. This is done via the Teardowns section of the site.

Very interesting stuff.

A great example of a teardown is for a service we use here at Patdek called Trello. Trello is an interesting product because it is so open-ended and there's such a wide range of potential users. And Trello does a good job at bringing in these users in bunches.