Ratatouille or moussaka? That's what I usually do with them. Though I have been known just to grill them and have with a salad.
Ratatouille is usually very low calorie. Just onions, courgettes, aubergines, tinned tomatoes (or fresh..though I used tinned), garlic, basil and little oil, salt and pepper. Generally fried in large chunks to give it texture. Too small and it all goes too mushy.
Do a google for quantities. I just add whatever I have.
Moussaka is one of our families favs. Again, do a google as mine is just a bit of that and a handful of this
I always add cinnamon to moussaka and it's lovely. Hey....I add cinnamon to everything
I don't salt the aubergine as Kate suggests. I used to years gone buy, but the aubergines these days don't usually need it. I do dry them after cutting though to get rid of some of the moisure.