A complete documentation is available that you can search from here :

Shortcuts

• Two minutes to get Sonar up and running
• Full Installation guide
• Getting started with Sonar

Use cases

• Unit Tests: Manage Code Coverage by Unit Tests with Sonar
• Integration Tests: Measure Coverage by Integration Tests with Sonar – Updated
• Duplication: Manage Duplicated Code with Sonar
• Code Review: Effective Code Review with Sonar
• Differential Services: Differential Services in Sonar for a Complete Support of Continuous Inspection
• Eclipse: Running local analysis with Sonar Eclipse 2.0
• Integration Tests : Bridging Internal and External Quality with Sonar
• Quality Model : SQALE, the ultimate Quality Model to assess Technical Debt
• Home Page : The new “Filters” functionality added in Sonar 2.2
• Multi-languages : Sonar has become a Multi-Languages Platform
• Code Coverage : Pick your code coverage tool in Sonar 2.2
• Continuous Inspection : Continuous Inspection Practice Emerges with Sonar
• Class Design : Clean Up Design at Class Level with Sonar
• Package Design : Fight Back Design Erosion by Breaking Cycles with Sonar
• Technical debt: Evaluate your technical debt with Sonar
• Authentication and Authorization: Securing access to projects in Sonar
• Sonar Time Machine : Learn how to replay the past
• Package cycles : Fight Back Design Erosion by Breaking Cycles with Sonar
• Coupling and Cohesion : Clean Up Design at Class Level with Sonar
• Portfolio management: bring a new dimension to Sonar with the Views plugin.
• Sonar Light : the low calorie mode for Sonar
• Unit tests : manage unit tests and improve code coverage
• Code Review: quality of Apache Sling using Sonar
• Continuous Integration: A Hudson plugin for a closer integration with Sonar.
• Having fun: The most sexy plugin of the Sonar forge

Others

• “Contrôler la qualité de ses projets avec Sonar”, a french article by Romain Linsolas.