There's one hundred and one recipes that start with a plain old can of tomatoes. Here's a delicious one I saw on Jamie at Home yesterday.
Simple Pizza Sauce
Handful of fresh basil leaves, roughly chopped
A few garlic cloves, sliced
One can of whole tomatoes
One can of tomato paste
1 tsp sugar
Heat some olive oil in a large pan. Add garlic and basil, saute for a few seconds. Add the can of tomatoes, break them up with the back of a spoon. Simmer for 5 minutes. Over a bowl, strain the sauce through a mesh sieve - use a spoon to push as much liquid out of the tomatoes. Discard the solids. Return the strained sauce to the pan, add the tomato paste, salt, pepper and sugar, and simmer for another 5-10 minutes, until the sauce has thickened.