Voki.com has it all! It's ideal for various school projects at any grade level. It has powerful and easy-to-use features to make personalized avatars with 150+ customizable characters and 500+ costumes. Students can record their own voice using a mic or phone, or type-to-speech and choose from various voices and languages. Have your students create avatars that talk about events in history, book reviews, vocabulary words and definitions, original writing pieces, outcomes of lab experiments, poetry, ...basically, whatever you want. The process of writing a script, knowing the content of what they are going to discuss or analyze, designing a customized avatar to match certain criteria, are all great ways for kids to use those critical thinking, evaluating, and analyzing skills while having fun at the same time.
Here's a voki that some crazy lady made where she recorded her own voice, but also inserted audio files downloaded off the net.

Enjoy!!