Export your WordPress blog to Tumblr.
Doesn't work, always gets an Internal Server Error.
It's not been updated since it's initial 0.5 release and I suspect it has fallen foul of the same API changes on Tumblr as the popular Tumblr.ize plugin has. Developer has ignored 3 support tickets raised in the past year. Think we can consider this dead, which is a shame as it would be a simple and elegant solution.