I am part of a volunteer-run non-profit that conducts workshops across a dozen countries countries, both online and offline.

What is a good way to store data about the workshops we did, who attended each workshop, in what capacity, who was awarded diplomas, etc?

We want to move away from online spreadsheets, or free (as in beer) software. We do have a server, on which we can install some software. But we want a minimal hassle system that gets the job done, so we can concentrate on our real goals.