Serious Eats: Recipes
Cook the Book: Baked Macaroni and Cheese
The omission of meat—rather than the inclusion of vegetables—is primarily what makes this recipe vegetarian. But who's going to object when it comes to mac and cheese?
The instructions below come from Mark Bittman's How to Cook Everything Vegetarian and include a basic version as well as some variations to fancy it up a bit. And there's at least one with some vegetable matter in it.
And, as always, you can throw your hat in the ring to win a copy of this book. Details here.