Helm is an Emacs framework for incremental completions and narrowing selections. It provides an easy-to-use API for developers wishing to build their own Helm applications in Emacs, powerful search tools and dozens of already built-in commands providing completion to almost everything. It is a must-have for anyone using Emacs as a main work environment. Helm has been widely adopted by many Emacs power-users. It is available in Melpa and can be easily installed from the Emacs package manager.
Helm in action searching with Grep Ag