[oops, I keep forgetting to add cl-pro email when replying.]

IMHO:

DSL can be made of a varying mix of abstraction, syntax and semantics. All of which can be achieved within CL using interpreter & compiler, macros, closures, reader macros, compiler macros, printing protocol and CLOS. These will help a lot,  both the developer and the user.

check the following examples:

Corman CL Assembler DSL (check the source code for assembler.lisp and how elegantly normal x86 assembler syntax was introduced into CL code) http://www.cormanlisp.com/index.html

SBCL VOPs: http://sbcl-internals.cliki.net/Adding%20VOPs http://paste.lisp.org/display/41937

GOAL: Game Object Assembly Lisp ("...intermix assembly instructions seamlessly with higher-level code...") http://www.gamasutra.com/view/feature/2985/postmortem_naughty_dogs_jak_and_....

CLSQL: SQL syntax

CL-Typesetting: typesetting DSL

Prolog interpreter or compiler.

those are the ones I remember directly when talking about DSL in common-lisp

- Ala'a