January
- Frode Vatvedt Fjeld announces Movitz
- Sven Van Caekenberghe announced the availabily of the KPAX web application framework
- ASDF-INSTALL ported to various places by Edi Weitz
- Planet Lisp begins
February
- Gary Byers releases OpenMCL 0.14.1, the first packaged release of OpenMCL with native threads
- Pierre Mai ports CMUCL to MacOS X
- Daniel Barlow begins an AMD64 port of SBCL; his initial enthusiasm for which lasts about two weeks
March
- Luke Gorrie creates the initial SLIME Manual
- CLISP 2.33 released
- Armed Bear Lisp becomes Armed Bear Common Lisp
April
- Dave Roberts starts Finding Lisp
- Jack Coleman starts Programming Languages, a Journey
- Common Lisp: An Interactive Approach is available online
- Antonio Menezes Leitao releases the first version of the Linj compiler
May
- Gary King starts unCLog
- bknr is announced
- Edi Weitz releases the initial version of tbnl
- Paul Graham's Hackers and Painters published
- Brian Mastenbrook announces Portable Araneida
June
- Franz announces a new regular expression API for Allegro CL
- Arthur Lemmens starts a Lisp user database
- Peter Herth releases Ltk, a Lisp binding to the Tk toolkit
July
- Franz announces a new Prolog implementation within Allegro CL
- Rich Hickey announces jfli
- The Libre Software Meeting 2004 in Bordeaux attracted many Free Lisp developers.
August
- Ben Lee releases the initial version of Elephant, a Lisp persistence system based on Berkeley DB
- Slime 1.0 beta released
- eboy.com re-launches, powered by cmucl and bknr
- CLSQL 3.0 released
- CMUCL 19a released, introducing dozens of new features and fixes
- Paolo Amoroso starts Lisp Propulsion Laboratory Log
September
- Christophe Rhodes starts work on Unicode support in SBCL (subsequently released in November 2004, in SBCL 0.8.17)
- SLIME 1.0 officially released
- Rich Hickey releases Lisplets
October
- Franz Allegro Common Lisp 7.0 is released
November
- Unicode support is added to the main branch of SBCL development
- Rick Taube releases lambda-gtk, an FFI binding to gtk2
- Mikel Evins begins the Skate project, an attempt to reproduce some of the functionality of the old SK8 environment
- Juho Snellman revives the SBCL port to AMD64. A (mostly) working SBCL for AMD64 is eventually merged in the first few days of 2005
December
- LispWorks 4.4 is released
- Conrad Barski creates a Lisp tutorial in comic form: Casting SPELs in Lisp
- Successful Lisp is published in book form
- Edi Weitz announces RDNZL, a Lisp library for interoperating with .Net