You want to help and contribute? Perfect!

These are some contribution examples

Reporting issues to the bugtracker.
Submitting pull requests from a forked icalendar repo.
Extending the documentation.
Sponsor a Sprint (http://plone.org/events/sprints/whatis).

For pull requests, keep this in mind

Add a test which proves your fix and make it pass.
Describe your change in CHANGES.rst
Add yourself to the docs/credits.rst