Layer Cakes - you can cut a standard layer cake recipe in half and bake each layer in a 6-inch cake pan.  Sometimes you have to play around with the shortenings, but this usually works.

Ice Cube Trays - and freezer bags are the solo cook's best friend.  Pick up some trays at a dollar store and use them to freeze extra sauce, stock, egg whites; all those unused portions that we always end up with.  You know - when a recipe calls for one tablespoon of tomato sauce and you have to open an 8-ounce can (the smallest you can find) and it's not likely you'll use the other 15 tablespoons before it goes bad.  The solution is to measure the extra into the trays, freeze them, then empty the frozen cubes into freezer bags.  I use this method with tomato sauce, adobo sauce, a stock I make from boiling left-over shrimp shells -- well, you get the idea.  Then when I'm making something 6 weeks from now that calls for one tablespoon of tomato sauce, I just grab a cube instead of opening another can. 

Gelatin is a Preservative (from Ron L. Henderson) - When you put it in soups or sauces gelatin acts as a preservative, without changing the character of the dish - except possibly making it a little richer.  When you refrigerate it, it becomes a gelatin salad and will keep for weeks.  If you reheat it, the vegetables are still crisp.