With motivation from algebraic topology, algebraic geometry, and string theory, we study various topics in differential homological algebra. The work is divided in five largely independent parts : I- Definitions and examples of operads and their actions II- Partial algebraic structures and conversion theorems III- Derived categories from a topological point of view IV - Rational derived categories and mixed Tate motives. V - Derived categories of modules over $E$ algebras. In differential algebra, operads are systems of parameter chain complexes for multiplication on various types of differential graded algebras up to homotopy, for example commutative algebras, $n$-Lie algebras, $n$-braid algebras, etc. Our primary focus is the development of the concomitant theory of modules up to homotopy and the study of both ical derived categories of modules over DGA's and derived categories of modules up to homotopy over DGA's up to homotopy. Examples of such derived categories provide the appropriate setting for one approach to mixed Tate motives in algebraic geometry, both rational and integral.