Free Beginner's 'Introduction to Mandarin' Tutorial
http://www.chinese-outpost.com/language/
news in bilingual texts
https://chinadialogue.net/en/
audio and video lessons
https://www.chineseclass101.com
Chinese Character Flashcards (Traditional Version)
http://animation.archchinese.com/arch_flashcard.html
The Red Brush project is a collection of texts in Chinese from a wide range of writings from Imperial China, by and about women writers. The website for this collection is available in both English and Chinese.
http://digital.wustl.edu/r/red/
This site contains Chinese classics with each character hyperlinked to its definition and etymology. No Chinese software is necessary - characters are displayed as images. Links to English translations are included for most works.
http://zhongwen.com/gudian.htm
Oxford University resources
http://www.ctcfl.ox.ac.uk/
flashcard type program for learning characters
https://remembr.it/
genealogy and dictionary of Chinese characters
http://zhongwen.com/
Conversational Mandarin Chinese Online
http://web.csulb.edu/~txie/ccol/content.htm
lists of tools to people who are already studying and using Chinese.
http://www.mandarintools.com/