libedit - Use the libedit library (replacement for readline)
libffi - Enable support for Foreign Function Interface library
libnotify - Enable desktop notification support
-libressl - Use dev-libs/libressl instead of dev-libs/openssl as SSL/TLS provider (ineffective with USE=-ssl), packages should not depend on this USE flag
+libressl - Use dev-libs/libressl instead of dev-libs/openssl when applicable (see also the ssl useflag)
libsamplerate - Build with support for converting sample rates using libsamplerate
libwww - Add libwww support (General purpose WEB API)
lirc - Add support for lirc (Linux's Infra-Red Remote Control)