You could make a plum crumble with cream.
You could roast them with maple syrup and serve them with thick vanilla yogurt.
You could add chili and onion with some spices and make a chutney. (ask if you want a recipe)
You can peel them and slice them. Pack at the bottom of a buttered oven dish. Cover with cake batter and bake. Serve slices of this with custard or vanilla ice cream.
You can blend them and mix with yogurt and some honey. Freeze in ice lolly molds and freeze for a summer treat.