Emacs is a general-purpose editor and the most widely-used environment for Common Lisp development.
SLIME is the most widely-used Common Lisp IDE.
Portacle is a portable and multiplatform development environment. It includes Emacs with Slime, SBCL, Quicklisp and Git.
Sly is a fork of SLIME.
SLIMV is a full-blown environment for Common Lisp inside of Vim.
Vlime is a Common Lisp dev environment for Vim (and Neovim), similar to SLIME for Emacs and SLIMV for Vim.
Dandelion is an Eclipse plugin for Common Lisp. It is available for Windows, Mac and Linux, has built-in support for SBCL and CLISP, an interactive debugger, and more.
SLIMA is a SLIME plugin to interactively write Common Lisp with Atom, helping turn Atom into a full-featured Lisp IDE.
Lem is a ready-to-use Common Lisp editor with an ncurses and Electron interface.
cl-repl is an ipython-like REPL for Common Lisp.