I am just beginning to learn Mandarin Chinese, so I found chapter 11 of Curtis J. Bonk's book The World is Open, fascinating in that it referred to so many online sites for language learning. In addition, my backgroundis in teaching second languages, so I was particularly interested to see what some of these sites offered.
I checked out beginning Mandarin at Live Mocha and was quite pleased with the presentation of material and exercises which incorporate visuals as well as both oral and written language. I haven't tried the interaction with a native speaker yet, but hope to do so when I have more of basic vocabulary. The ability to converse with a native speaker is an ideal situation for language learners. However, the conversational exchanges that occur during these situations can vary tremendously. The key to success would be finding a partner that fit your needs in terms of language proficiency, choice of topics, and patience on both ends of the dialog!
The Mixxer Language Exchange which utilizes Skype also looked appealing especially since it offers teachers the ability to create groups and exchanges can be either in written form or through Skype.
Friends Abroad is now owned by Babbel and offers courses that can be purchased, but does not offer Chinese. About.com owned by the New York Times does offer free lessons in Mandarin Chinese.
Chinesepod is described quite well in chapter 11. I like the fact that it has a mobile app. but wish the transcripts were free.
As the summer progresses, I hope to check out each of these sites in more detail. In the meantime, I am also using these online resources in my study of Mandarin:
Mango (Online Chinese course from Montgomery Co. Public Library)
On home page click Language Learning Tools, then Mango languages
Pinyin Chart with audio pronunciations of initials and finals
List of free Chinese classes on iTunes
List of Chinese resources on the web
BBC Chinese lessons with videos and transcripts
List of links to videos for learning Chinese including Benny's "I Like Chinese"