A nice entry point into the literature on calculus of relations is Roger D. Maddux's The Origin of Relation Algebras in the Development and Axiomatization of the Calculus of Relations. This historical survey will take you from the pioneering work of Pierce and Schröder up to more recent work by Jonsson, Lyndon, Monk, Tarski and others. Chasing references to the works in the bibliography will lead you to more recent work.
Also see Uta Priss' An FCA interpretation of Relation Algebra for (pointers to) connections of relation algebra and the relational algebra in database theory.