~/.config/kactivitymanagerdrc is the main configuration file for KDE Activities.
In the section [activities], there is the list of all activities, with a hash, the machine name for the activity, and the activity's human name.
E.g.:
[activities]
01a40fef-c0c7-4050-b9a6-0cedd8546608=Main
a7ceb07c-d66f-4a8d-bf08-27777b29b083=KDE
// etc.
See:
http://linux.overshoot.tv/home/user/.config/ksmserverrc
http://linux.overshoot.tv/wiki/plasma_activities
