Golden Retriever? I know some can be a little hyper, but we had a Golden that was very calm, friendly, loved other dogs and loved people.
Some of the large breeds (like Great Pyrenees and Newfies can also be very calm, although they may not meet your activity criteria Most of the Greyhounds I've met are very sweet and mellow, so that's another possibility. Or you could get a rescue dog. If it's older, you know how its going to turn out and what you're getting.
I suspect there are dozens of breeds that would fit your criteria and ultimately it's up to you to narrow down the choices to those breeds whose size, appearance, etc. appeal to you.