Adalanche gives instant results, showing users' and groups' permissions in an Active Directory. It helps visualize and explore who can take over accounts, machines, or the entire domain and can be used to find and show misconfigurations.
Active Directory security is notoriously difficult. Small organizations generally have no idea what they're doing, and way too many people are just added to Domain Admins. In large organizations, you have a huge number of people with different needs, and they are delegated access to varying degrees of power in the AD. Someone makes a mistake at some point in time, which can cost you dearly.
Source code and additional information may be found here: https://github.com/lkarlslund/Adalanche