How to: Integrate Disqus manually on Blogger/Blogspot
Once again, the community lends us a hand. This one comes from Laibcoms (thanks!).
We recommend only advance users and tinkerers attempt this one. If you’re having any problems with our Blogger integration tool, try this guide on manually editing the template.
Of course, we do plan on releasing an improved integration tool in a near-future release.
[UPDATE] Laibcoms also has another guide for integrating Disqus with Blogger classic templates.