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.
Atom-Slime is a SLIME plugin to interactively write Common Lisp with Atom, helping turn Atom into a full-featured Lisp IDE.