Chinese with Mike - Awesome weekly Chinese video lessons
Chinese Internet Radio - Listen to free radio streaming from China
Lao Kang's Mission - Set of iOS apps that help strengthen your tone and pinyin recognition
All Mandarin- Quality Mandarin lessons from native Chinese speakers. Learn Mandarin online now!
Pinyin Joe - Teaches Pinyin input methods for Western-language computers and smartphones
Learn Chinese Weekly - Various tools including learning Chinese through song and rhymes
Chinese Hacks - Tips, Tricks, and Lessons for learning Chinese
Mandarin Tools - Various tools to aid in Chinese study
Chit Chat Chinese - Chinese learning textbooks, audio and other resources
Pinyin.info - Website aimed at contributing to a better understanding of Chinese language
Study More Chinese - A community project to build a free Chinese learning website

Writing Chinese:
Skritter - Focused learning tool for how to write Chinese and/or Japanese.
ShuFa West - Chinese calligraphy resources for the non-native enthusiast

More Resources:
Social Mandarin -Social bookmarking site that aims to collect Chinese learning resources online
Marjorie Chan's China Links - Annotated links to over six hundred China- and Chinese language and linguistics-related websites

Noted Blogs of Chinese Learners:
Mandarin Click by Click Blog - Recommended blog with great, relevant articles for the Chinese learner
Lingomi Blog - Very interesting blog about improving your listening and pronunciation skills
En Route to Fluency - Follows the journey of a student of Chinese