cl-digraph is an implementation of a mutable directed graph data structure for Common Lisp.
cl-digraph focuses on simplicity, correctness, and usability. Performance is not terrible, but is not a high priority.
It is currently not thread-safe, but this may happen in the future.
The test suite currently passes in SBCL, CCL, ECL, and ABCL on OS X and Debian. Further testing is welcome.