Our school has been using Lingtlanguage.com. It's free, the quality of the recording is good, and it does not require you to download anything between computers. You can post written prompts, pictures, videos, or audio prompts. You can choose to have students respond in writing or with a spoken response. Once they finish, they put in their email. You access the file by going to your teacher page, clicking on their response, and listening/reading it. Then you can provide feedback directly to them, either in writing or by recording it. The feedback is sent to the email that they provided as a link.
Hope that helps!