• Michael Barr's diagxy package designed for general usability in a variety of mathematical disciplines;
• François Borceux' package which is specifically aimed at category theory diagrams;
• the circ circuit-diagram macros; Pedro Quaresma's dcpic macros for commutative diagrams, using LaTeX picture mode;
• Anders Svensson's kuvio macros for commutative diagrams, using dvips “PostScript \specials”;
• Paul Taylor's long-established commutative diagram macros, which are designed to provide high power in a standard (La)TeX environment; and Kris Rose and Ross Moore's xypic package which can be used for a variety of graphs and diagrams.

The author is The CTAN team.