World Learner Chinese provides 15 minute audiocast Chinese lessons. The majority are basic level lessons - Buying a Bookcase, Do You Like Small Animals? , A Bit Swollen...

The Intermeditate lessons are a bit more, topical, I guess - A Mother's Postpartum Rest, Factories and Exhaust, Environmental Protection, Martial Artist and Have You "Been" Hit?

The dialogues are not as dry as the titles may suggest and a good deal better than most textbooks that I've seen. The dialogues for all levels are reletaviley short. Which I believe is good, as I will explain in a moment. There are three readings followed by a sentence-by-sentence parsing. Two instructors, one Taiwanese and one Western, explain tones, tone changes, vocabulary and it usage. In the intermediate lessons you get the added benefit of listening to the Taiwanese instructor explain these things in Chinese. So, actually, you are getting two short lessons in one. Memorization of dialogs can be helpful, but much more useful is listening to how native speakers describe and explain, much more valuable skills. What are you gonna do when you don't have the word that you want to use in your vocabulary? If you have the skills to do so, you explain it. If not, you ( like many students) say sorry and shut up.

I would recommend this site for learners up to the mid to mid-high intermediate level, if only to polish up some of your syntax and pronunciation. I mentioned that the dialogues were short. That's fine. We don't need to be overwhelmed. Language learning theory, according to Krashen, states that we need comprehensible input, i.e., input that is just a tad over our current level. Comprehension comes before production (speaking, writing) for every language learner , native languages included. Therefore the more input we process, the more that becomes available for output. Our passive skills, listening and reading, will always be greater than our productive skills so it is important to keep topping off the tank.

Bonus - Is Your Chinese Better Than an Australian Prime Minister's?

Here is Prime Minister Rudd speaking Mandarin in an interview. Even when the reporter uses English, he sticks to Mandarin. Click and scroll down to view. You could YouTube P.M. Rudd, but go to this site and look around.