AD Info is a free reporting tool currently in Beta.
Download the installer, install it, and run the first report.
It has a good and easy to use user interface,
and many reports including User,Group, Group Policy, Computer, Contacts.
It automatically detected the domain and used the credentials I was logged in as by default to run the reports.
While domain and credential configuration options are available,
You didn't have to configure anything to run your first report.
It allows you to create custom reports. When creating a custom report I noticed that some of the attributes were marked as not available in Beta. I did not notice any bugs, but a warning dialog does mention upon startup that this is a Beta version and that there could be lots of bugs.
This is the second free Active Directory tool developed by Chris Wright. His other free tool is worth reviewing too.
It allows you to find and clean up user and computer accounts that are no longer in use.
Both AD Info and AD Tidy can be downloaded from download