I've managed to divest myself of most Google Apps. At this point I'm only using them for shared docs or calendars.

I recommend fastmail for calendars. Its pretty convenient, if you host your mail there already. CalDAV is really nice too so you can use your fancy calendar management apps, like thunderbird or outlook.

Shared docs I haven't cracked yet but I haven't needed to. But I hear nextcloud can do it. But that's a whole can of worms.