Digital story telling - stories are a great way to help students improve their language ability - this gives them a way to create something around that. This tool is more focused than Voicethread, and as a result less flexible, but still provides a similar experience and functionality.
Here is another good site with an overview of features of voicethread. This site also offers a great deal of handouts of how to guides, teacher tips, and examples etc. The table of contents for this site is as follows:
Using Voicethread for Digital Conversations
Unrelenting Desire to Interact
What is Voicethread?
Planning a Voicethread
Commenting Tips for Voicethreaders
Sample Strand of Comments
Assessing Voicethread Participation
Teaching Students to Create and Moderate Threads
Sample Voicethreads
Voicethread Handouts
Voicethread Overview
Voicethread Do's and Don'ts
Tips for Teachers
Copying an Existing Voicethread
Previewing a Voicethread
Commenting on a Voicethread
Commenting Language
The Cultural Photograph
Welcome to Our World
Powerpoint Template for Quotation Voicethread
The Holocaust and Hitler's Youth Template
Scoring Student Participation in an Asynchronous Conversation
Sources for Images
Citing Images