The group I currently play with uses a group chat over SMS/MMS. But I'm going to be DMing a campaign with an open table, so I need something more persistent and flexible. I've used Discord in the past but IMHO it has way too many features.
What have you used to keep in touch with your players?
We use discord. My group is actually about 4 groups connected together with overlapping players, so it's a place we can all congregate virtually. We have a channel for scheduling, ones for in-game content, and some for just messing around.