Use email to validate post, not unlike craigslist I'd like for anonymous users to be able to post nodes to my site. By default their post is unpublished, but when they submit it, the site sends an email with a verification URL. When they revisit the site with that URL they can then publish their node.

Call this the 'craigslist model.' :-)

Restating: I want users to be able to publish their own node anonymously, by linking out of an email.

I've been unable to find a module or setting that does this, and I thought I'd ask before diving into code.

Update: Found this unmaintained Drupal 5 project: Anonymous publishing.

Similar question: How can anonymous users be allowed to post while still maintaining content integrity?
You can use the Rules module, but you'll have to write a custom rule to grab the email from the submitted node and send a verification link to the email address. You could also do this with a custom function through hook_entity_insert().

For the verification link you could do use drupal_hmac_base64() to create a url-safe hash of the content of the post or of the node + timestamp + email or something like that. 

Then you can create a custom menu to fire a callback function that takes arguments from the verification link to publish the node if the verification link is correct.