wrote directions on how to deal with it. Yesterday, Posterous made its official announcement that it will be shutting down on April 30. The announcement includes some directions on how to export your data. You can also follow my annotated screenshots of the process. (click the images to view them in full size)
Step 1: Sign into your Posterous Spaces account and select "backup."
Step 2: Select the blog(s) that you want to backup.
Step 3: Enter captcha code and your email address to be notified when your backup is ready.
Step 4: Download zip file containing the contents of your blog.
One of the great things about Posterous was that students could post to a group blog via email. That option is also available in Blogger. You can learn how to set that up in Blogger in my post here.