Hi,
As for invitations for employees - we don't send invitations to them, you just assign them to a phone call, a meeting, task, etc. The user simply logs in to epesi and on the Dashboard he/she will see all assigned activities.
We will include at some point invitations - but this will apply probably only to a calendar - an e-mail will be sent to invited users with a link to the page where the meeting will be confirmed or not and with a link to iCal formatted data.
As for resources - yes, we do have something like that, it has been custom built for a school where you can put on the calendar a lesson and combine resources: students, teachers, rooms, programs.... We would love to design a general purpose engine for different kind of resource scheduling - but because of our limited resources we create modules like this on a case by case basis.