Posterous, which was long Tumblr's main competitor in the Tumblog space before Twitter bought it out, is shutting down in April. More:

Posterous launched in 2008. Our mission was to make it easier to share photos and connect with your social networks. Since joining Twitter almost one year ago, we’ve been able to continue that journey, building features to help you discover and share what’s happening in the world – on an even larger scale.

On April 30th, we will turn off posterous.com and our mobile apps in order to focus 100% of our efforts on Twitter. This means that as of April 30, Posterous Spaces will no longer be available either to view or to edit.

Right now and over the next couple months until April 30th, 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.
4. Return to http://posterous.com/#backup to download a .zip file.

If you want to move your site to another service, WordPress and Squarespace offer importers that can move all of your content over to either service. Just remember: you need to back up your Spaces by April 30.

We’d like to thank the millions of Posterous users who have supported us on our incredible journey. We hope to provide you with as easy a transition as possible, and look forward to seeing you on Twitter. Thank you.

Sachin Agarwal
Founder and CEO

There were a lot of signs this was going to happen, most notably the late appearance of the export tool mentioned above.