Posterous is closing on April 30, 2013. After this date, your spaces will no longer be available online.

Right now until May 31, you can download all of your Posterous Spaces including your photos, videos, and documents. 

Here are the steps:

1. Go to http://posterous.com/#backup.
2. Click to request a backup of your Space by clicking “Request Backup” next to your Space name.
3. When your backup is ready, you'll receive an email. If you don't receive an email, check back on the backup page.
4. Return to http://posterous.com/#backup to download a .zip file.