If you're looking for a frozen dinner, you may even find one that's marked specifically gluten-free Glutino makes some prepared meals, as does Amy's Kitchen. Don't purchase a frozen meal unless it's specifically marked "gluten-free," since most of those that aren't labeled do contain gluten ingredients.
You also may be able to find some prepared foods in the dry-goods section of the supermarket that are marked gluten-free for example, I've seen "just add water" pre-made Indian or Thai dishes in the ethnic foods section of the store. Thai Kitchen is one brand that makes some gluten-free dishes you could eat as a meal.
Frozen pizza fans have plenty of gluten-free frozen pizza options, including vegan products and some that are gluten-free and casein-free. Many grocery stores stock at least one or two of these in my local store, they're in the "natural" foods freezer section, which is separate from the regular freezer section.
Canned Soups: A Few Options Available
People new to the gluten-free diet often are surprised to learn that canned soups frequently contain gluten the flour is used as a thickener, especially in "cream" soup products. However, it's possible to find some canned soups that are gluten-free.
Progresso makes some gluten-free soups, as does Pacific Natural Foods (which packages its soups in boxes, not cans). Some gourmet soup manufacturers, such as Bookbinders Specialties, also make some gluten-free soup options, but you'll have to read labels and possibly make some calls to determine what's safe and what's not.