Switch the Front-End Language With ?lang=
Lets visitors switch the theme and plugin interface language with a ?lang=fr_FR link; the choice is remembered in a cookie and limited to languages you allow.
Snippet Library
Multilingual snippets for WordPress
Snippets for multilingual sites: language switchers, translated strings and per-language behavior with WPML, Polylang and similar plugins. For sites that serve readers in more than one language.