Topic: Lisp
John Wiegley's ledger is a popular double-entry accounting system with a Unix command line interface.
What many people don't know is that version 3 of ledger was written in Common Lisp. This version was never made into an official release. In a FLOSS weekly podcast, Wiegley explains (31:00) that Common Lisp was not the best choice for ledger's users.
I emailed John to learn more about this. He replied that there were only two major problems: building cl-ledger was more difficult than building ledger, and that cl-ledger could no longer be scripted from the command line. In effect, the Common Lisp REPL had stolen the place of the Unix command line as ledger's interface.
cl-ledger was written in 2007, and there are now good solutions to these problems. ASDF works well as a build system, but before Quicklisp, dependency management for Common Lisp applications was difficult. Quicklisp solved the biggest outstanding problem in building Common Lisp applications. (PS - you can give Zach a Christmas gift for his work on Quicklisp)
Didier Verna's Command-Line Options Nuker is a full-featured command line interface library for many implementations on multiple platforms.