Simple things to do with very tart plums? We got a bag of purple plums from our CSA that have a great flavor and seem ripe, but that are very tart. I'm the only person in the family who really likes sour fruit, and they are pretty sour even for me, so we are not going to get through them eating them out of hand.

What are some good fast and simple ideas for cooking them? A compote? Can I make something like apple sauce?

EDIT: Speed and simplicity are important considerations. Homemade jam is delicious, and I know how to make it, but jam-making isn't something I am going to do after I get home from work to use up some extra fruit.
Tart fruits work well in jellies and jams, or as candied fruit. These all allow you to vary the sugar content to get the level of sweetness you want, plus you don't have to worry about botulism as much.

You could also try a fruit-infused brandy: cut fruit into slices, and layer fruit/sugar/fruit/sugar into a tall lidded jar. Cover with a spirit of your choice, usually vodka, although a milder brandy or white rum also works. Let this sit for several weeks to infuse, strain, and use as a flavoring in cooking or as a mixer in cocktails (or just drink it).