After December 17th, Tumblr no longer allows adult content. To help out other Tumblr refugees, I've put together a big list of alternatives (see below). Everyone can vote for their favorites and the results are sorted in order:)

How to Backup your Tumblr - this post on ErosBlog has a great guide on how to backup your Tumblr. It involves using a free tool to download your posts and images.