Here's another cute way for kids to communicate with an audience. Baby Mail allows them to write a message, perhaps for Grandma or a friend, and either record themselves saying it via microphone, or else type it into the text box and have the site say it. That's how I made my example below. Once you choose a baby to deliver your message, you have the option of getting the url, sending via email, or grabbing the html code the way I did, so you can embed it on your blog or website.
(Thanks to the incomparable Larry Ferlazzo for the idea!)