Common Lisp Library Audience Expansion Toolkit
FFI

CLAUDE (the Common Lisp Library Audience Expansion Toolkit) exports libraries written in Common Lisp, so that applications being developed in other languages can access them. CLAUDE co-operates with foreign runtimes in the management of CLOS objects, records, arrays and more primitive types. Lisp macros make the task of exporting a library simple and elegant; template documentation along with C headers and sample code files relieve some of the burden of explaining such exports to the application programmer.

http://www.nicklevine.org/claude/