We usually do a short retreat once per year. It starts around 9 am on a Friday, when we drive with a bus to our destination (usually 2 or 3h drive), and we come back on Saturday about 3 pm. All of that is "fun time"/team building. Of course that's a bit lamer than the topic, but since many of us have kids (I don't) they have a more realistic chance of attending. And for most them usually works out (but were quite small with ~50ppl).

My SO's employer went to Mallorca to party for a week when the company was smaller (200ppl?). I like our approach much more.