L'echo des galets, a creperie near Printemps on the Presqu'ile. Reasonable prices, and great menus for lunch and dinner including salads, savory crepes, and desert crepes. Have them with a bolée of cidre breton.
Restaurant Thomas on rue Laurencin if you are looking for something a bit more expensive. It is cozy, the service is excellent, and the house specialty pain perdu is to die for.