How can I create user profiles in drupal 7? I would like to know how to create a user profile (registered user block) similar to the one on this site. I am using Drupal 7 and the Zen theme.
In Drupal 7, users accounts are fieldable entities like nodes. From Administration » Configuration » People » Account settings, you can add fields and configure their display on the user page (ie. /user/$uid). 

For a more complex setting with multiple profile types and separation of accounts (ie. user) and profiles, you can use the Profile2 module.

You can then use Views to easily crate blocks and pages to list users and information from their profiles.