Reefknot is a set of Perl modules and scripts intended to make it easy to implement RFC-compliant calendaring and scheduling applications. For more on the modules we're planning to build, you might want to read the Reefknot Developers' Roadmap.
It is likely that example applications will also be built as part of this project.
iCalendar is the name given to the set of data formats and protocols released as RFCs by the IETF Calendaring and Scheduling working group. These include:
RFC2445: Internet Calendaring and Scheduling Core Object Specification (iCalendar)
RFC2446: iCalendar Transport-Independent Interoperability Protocol (iTIP)
RFC2447: iCalendar Message-Based Interoperability Protocol (iMIP)
Related documents currently in draft include the specification for a Calendar Access Protocol (CAP).