Free Chinese Courses

Lessons complete with audio (and/or video), new vocabulary, dialogues, focus on characters and pronunciation
Busuu: a website and an app for learning languages, a mixture between premium and free. You canlearn Chinese by topic, practising vocabulary, speaking, listening and writing. You can go step by step through the different levels.
FSI Mandarin Chinese lessons: a complete course with textbooks and audio
Practical Chinese Reader with vocabulary lists for it. 
China Radio International
BBC Chinese
Clear Chinese: 15 lessons with basic phrases, audio and practice section.(!The listening is a bit clumsy)
Confucius Institutes Online offer the opportunity to learn about China and its language online. Browse through the website to find interesting articles and online lessons.
I Love Learning Chinese - for beginners
★ Study Chinese with real world video content
Rudgers University: 80 units in 4 levels; lessons in Chinese with English translation and pinyin for the lower levels, grammar and vocabulary explanations for all.
Zhongwen Red: lessons centered around a vocabulary unit that is presented in the context of several example sentences, then expanded upon by a short dialogue, complete with audio.
Overseas Chinese Language and Culture Education: entire levels, complete with a book for the teacher and an exercise book