Findutils

helm-find uses GNU find to search for files in a directory hierarchy.

Usage

Execute helm-find (bound to <helm-prefix> / by default). The search with this command is actually performed literally, however you can use a space to match multiple pattern within a line.

From helm-find-files

Hit C-c / while using helm-find-files.

Other platforms

Windows

On Windows, you need to install the MSYS version of find because the GnuWin32 version is not working.

The MSYS version of find is not available as a standalone program; it must be installed as part of MSYS, which is installed using the MinGW installer. Steps are as follows:

1. Download and install the MinGW installer.
2. Install find with the installer.
3. Add MSYS bin directory to PATH (e.g. C:\MinGW\msys\1.0\bin).

I believe MinGW itself does not have to be installed, but I could be wrong.