Introductions, Tutorials (start here)

• Working with OMNeT++: Flow Chart
• Overview of the Simulation IDE (pdf)
• Getting started with the IDE (screencast)
• A 10-minute introduction into OMNeT++
• TicToc tutorial

Community content

• OMNeT++ 4.x Wiki page

Documentation

• User Manual (pdf)
• IDE User Guide (pdf)
• API Reference
• other: Parallel Simulation API, NEDXML API
• Install Guide (pdf)
• Migrating simulations from the 3.x version (pdf)
• IDE Developer's Guide (pdf)
• IDE Customization Guide (pdf)
• Change Log

Related

• Asking for help on the mailing list
• OMNeT++ Bugtracker
  
• Wizards for the OMNeT++ IDE (pdf - slides) (OMNeT++ Workshop, March 19, 2010, Malaga, Spain)
• Parallel distributed simulation with OMNeT++