Recordr is a super easy to use nice site for recording audio/video and then uploading it to the web. Once you record your media, you can then either directly link it to Twitter/Tumblr, or get an embed code to put on your site/blog. No registration is necessary which makes this a very easy application to use w/ students.
Below is my example...
Give Recordr a try by clicking here.
For another in depth review, check out Larry Ferlazzo's blog.