NTW Lisp is a server written in Common Lisp for applications that use the NTW protocol to communicate with a GUI client. This asynchronous protocol makes it possible to serve remote applications that are indistinguishable from native ones. It's also useful for quickly writing GUI apps from Common Lisp that can be run locally.
Allegro Common Lisp is a full ANSI Common Lisp (1994) implementation. It contains many extensions, including 32- and 64-bit native compilation, efficient built-in memory management, foreign functions (for interfacing with other languages), multiprocessing, UNICODE and locale support, XML/HTML parsers, a Web client and server, GTK+ interface (1.2 and 2.0), Java interface, OLE interface (Windows only), profiler, regular expressions, an XML RPC implementation, native Lisp RPC, sockets, DLL and shared library support, and more.