What do you have on hand?
My favorite use for plum sauce is to combine it with some Sriracha, rice wine vinegar and toss it with some shredded cabbage and julinned carrots.
If I have bok choy on hand, and Shitake mushrooms and some firm tofu, I'll combine and braise them using plum sauce.
If you want to go fusion, try making some Chinese crepes, stuff with chicken, cucumbers, carrots, scallions and plum sauce for a Asian inspired burrito.
It's also good in soups. Make yourself a nice corn chowder (hey, it's in season!) and then drizzle with plum sauce. Works well with cucumber soups as well.