One direction which is of particular interest to us and to many of the people we've spoken to is project management, another application field in which there is no prominent open source candidate.
To the best of our knowledge, there is not currently a standard or specification for handling project management data. It seems likely that we will have to develop this specification if we choose to extend Reefknot along these lines.
Some users have expressed a desire for integrated contact management, as exemplified by the Windows application "ACT". This is another area which will probably warrant further investigation and development.
We hope that third parties will build upon the Reefknot project to extend its utility into other languages or to create custom applications. We see potential for a wide range of calendar backends and servers (Oracle, MySQL, LDAP, HTTP, SMTP, WAP...) and clients (WWW, X11, Windows, email, PalmPilot...), and will be encouraging others to develop these.