Thanks for the circletimekids suggestion!
Though they are more for books and dvds than online learning, I use:
http://childbooks.com (excellent personal customer service)
http://asianparent.comhttp://bogeji.com (actually an ebay store, but she has inexpensive shipping, very fast. I have gotten all of the Dora dvd 5-disc sets from her, and we learn tons of Chinese from them. Also Pororo and the BBC's Little Robots)
http://chinasprout.comhttp://www.poppingpandas.com (montessori based)
http://www.mymontessorihouse.com/Montessori_Mandarin_Chinese_for_Children_Bilingual.htmlhttp://chineseforsmartkids.comhttp://chinese4kids.net (culture cubs dvds)
http://www.meimeiandme.comhttp://www.little-linguist.co.uk/category-144.htmlwww.myearlystart.com/ (Baobei the panda dvds: we got them with free shipping to Canada, ordering the set)
www.betterchinese.com (My First Chinese Words books and cd: we got the set. They also have online learning that go with the books and an online story library)
That's all I can think of for right now!