Here's an easy substitute if your favorite recipe calls for a can of condensed Cream-of-Something-Or-Other soup.
2 Tbsp butter
2 Tbsp flour
1 cup milk
boullion cubes/powder or soup base for 2 cups of liquid.
Make a roux: melt the butter over low heat, stir in the flour and soup base, and cook for 3-5 minutes until the mixture just starts to darken and has a nutty aroma. Stir in the milk and raise the heat, stirring until it comes to a boil and thickens.