Currently, threads are supported in sbcl under GNU/Linux, cmucl on x86 (on Linux, FreeBSD and OpenBSD), openmcl on OS X and Linux, ecl on all platforms and OS-es including Linux, Windows, *BSD, Solaris, OS X, and in some commercial Common Lisp implementations.
There are also thread compatibility layers.
- actors - Actors is an actors package for LispWorks
- Bordeaux-Threads - Bordeaux-Threads is a library to write multi-threaded applications in a portable way
- bt-semaphore - simple semaphores for bordeaux-threads
- chanl - ChanL is a concurrency library built on top of bordeaux-threads that provides channels as thread-synchronisation primitives
- cl-actors - A simple Common Lisp implementation of the actor model of concurrency
- cl-muproc - CL-MUPROC is an Erlang-inspired concurrency library available under the BSD license for Lispworks, OpenMCL, SBCL, CMUCL, and ACL
- common-lisp-actors - common-lisp-actors is a simple and easy to use Actor system
- erlangen - erlangen is a distributed, asynchronous message passing system for Clozure Common Lisp
- green-threads - GREEN-THREADS is a portable library implementing green threads (lightweight, cooperatively multitasked, user threads) in Common Lisp
- memento-mori - memento-mori is a library for writing robust, actor-based systems
- patron - Patron is a multi-consumer/multi-producer thread pooling library written
- Portable-Threads - Portable-threads is the GBBopen project's portable-thread code all packaged up for ASDF-Install
- Q-THREAD-POOL - Q-THREAD-POOL is a very simple thread pool implementation based on JPL-QUEUES
- sb-cpu-affinity - sb-cpu-affinity lets you set Linux scheduler CPU affinity masks from SBCL
- thread-pool - thread-pool is library that allows asynchronous function execution from a static thread pool
- threading-queue - threading-queue is a CL macro to distribute work on several threads, feeding the data via thread-safe-queues over several steps
- Also, McCLIM provides a thread compatibility layer in the CLIM-SYS package.