Mention cffi use in the README

README.rst

@@ -33,6 +33,9 @@ Anything that needs C code to be parsed. The following are some uses for
 * Automatic unit-test discovery
 * Adding specialized extensions to the C language
 
+One of the most popular uses of **pycparser** is in the `cffi
+<https://cffi.readthedocs.org/en/latest/>`_ library, which uses it to parse the
+declarations of C functions and types in order to auto-generate FFIs.
 **pycparser** is unique in the sense that it's written in pure Python - a very
 high level language that's easy to experiment with and tweak. To people familiar
 with Lex and Yacc, **pycparser**'s code will be simple to understand.