This site has a formidable amount of quality Mandarin Chinese language-learning resources.
The text above from their site sums it up quite well.
Wow! What a nice site.
"Online mandarin courses, chinese dictionary, chinese calligraphy studio, chinese name translation, chinese songs, chinese poems, chinese editor, chinese annotation tool, chinese dictionary, converters for pinyin, unicode, traditional and simplified chinese, tools to build chinese websites, etc..."
Mandarin Chinese Language Resources