Get List of available clans/groups

We are currently implementing a system into an app that is basically a clan system, however I didn't see (maybe overlooked it) a way to list available groups or get a sample of available groups.

I saw the getGroup call, but that appears to be for a single group and requires one to pass in the entityKey. I would like a way to simply do a call and have it return 25 groups or so, maybe with an option to choose a different set so the same group isn't always coming up if there are multiples.