ChinesePod offers Chinese language lessons in convenient fifteen minute podcasts so that you can practice language anywhere. Registration is required, and for seven days after you register you get all the benefits of a paid subscription, which include downloadable PDFs (so you can practice reading), flashcards, lesson exercises, and review materials. After the trial ends you can continue as a free user which allows you to listen to the podcasts and participate in discussion with other Chinese language learners.

Update: May not be free or accessible after the trial period. Beware if it asks for your credit card information, as websites tend to do automatic withdrawals after the trial period if you don’t terminate your account.