the study of cohen-macaulay rings and modules has been a central topic in commutative algebra for many years. among other things, they have played a major role in the investigations of the "homological conjectures", a set of problems on finite projective dimension, intersection theory, and related subjects. more recently, as a result of advances in the homological conjectures and developments in arithmetic geometry, a number of questions have come up about "almost" cohen-macaulay modules and algebras. in this talk i will give some background to these topics, discuss what almost cohen-macaulay algebras are and why they are interesting, and present various recent developments and open problems in this area.