We set up the projector in the backyard. The neighbour's dog joined halfway through.

The setup took about 40 minutes longer than it should have because we couldn't agree on where to point the projector, but once it was running it was genuinely one of the better evenings we've had. We picked a film we'd both already seen and loved, which meant we spent as much time quoting it to each other as watching. The dog from next door appeared around the third act, sat down like she'd been invited, and stayed until the credits. You don't need anything special for this — a decent projector (we borrowed one), a white sheet, and a choice not to stress about the quality. The whole thing cost about $12 including the popcorn.