Off leash runs/walks. Preferably somewhere secluded/not a dog park, but I do take my dogs to dog parks regularly because I don't have a lot of other options. But we stick to ourselves in quieter areas. If I had a car, and a better sense of direction, I'd love to hike with them constantly too.
If I'm feeling lazy or crunched for time, I'll take everyone except Keira (who doesn't understand or enjoy playing with toys) to a nearby field for a game of fetch.
And it's not my preferred method, but I do like that my dogs can also wear eachother out in the yard together wrestling.