In this survey, we outline two recent constructions of free commutative integro-differential algebras. They are based on the construction of free commutative Rota-Baxter algebras by mixable shuffles. The first is by evaluations. The second is by the method of Gröbner-Shirshov bases. 1 2 XING GAO AND LI GUO The study of differential algebra began with Ritt's classic work [35,36]. After the fundamental work of Kolchin [33], differential algebra has evolved into a vast area of mathematics that is important in both theory [15,44] and applications: for instance, in mechanic theorem proving by W.-T. Wu [45,46]. Free (commutative) differential algebras, in the form of differential polynomial algebras (Theorem 2.3), are essential for studying differential equations, as polynomial algebras are for commutative algebras.The algebraic study of integrals came much later. In fact the development did not start from an algebraic abstraction of integrals, but from the effort of G. Baxter [5] in 1960 to understand a formula in probability theory. As a result, the concept is not called an integral algebra, but called a (Rota-)Baxter algebra (Eq. (3)) which is the integral counterpart of the derivation, the difference operator, and divided differences (see Eq. (1)). Soon afterwards Rota noticed its importance in combinatorics and promoted its study through research and survey articles (see e.g. [40,41]). Independently, Rota-Baxter operators on Lie algebras were found to be closely related to the classical Yang-Baxter equation [42]. Since the turn of this century, the theory of Rota-Baxter algebra has experienced rapid development with broad applications in mathematics and physics [4,21,29,40,41,42], especially noteworthy in the Hopf algebra approach of Connes-Kreimer to renormalization of quantum field theory [16,19,29]. Here again a fundamental role is played by free (commutative) Rota-Baxter algebras that were first constructed by Rota [40] and Cartier [14], and then by in terms of mixable shuffles (Theorem 2.4).The fusion of differential and Rota-Baxter algebras, motivated by algebraic study of calculus as a whole, appeared about five years ago. It is amazing that two structures for this purpose were introduced at about the same time. One is a relatively simple coupling of differential algebra and Rota-Baxter algebra through section axiom (Eq. (4)) that reflects the First Fundamental Theorem of Calculus. It is called differential Rota-Baxter algebra [26]. The other one is a more faithful abstraction of the integration-by-parts formula (see Eq. (7)), giving rise to the concept of an integro-differential algebra [37] which has generated much interest [1,2,38,39]. As suggested in previous cases, free objects for these algebraic structures are important in their studies. Because of the relative independence of the differential and integral (Rota-Baxter) structures in a differential Rota-Baxter algebra, the free object was constructed by a clear combination of the free objects on the differential and Rota-Baxter sides and were obtai...