I've written a small bit of jQuery based code to take <pre> tags with certain markers and upgrade them in place into pretty embedded gists. The idea is that the tag int the blog post is a <pre> instead of a <script>.
Unfortunately you may have noticed my blog was supposedly in violation of the TOS for the past few hours. I suspect this is due to adding this script. It has now been unflagged but if you'd like to use it be aware that Blogger didn't seem to like it much at first.
Here's how I embed a gist now:
<pre class="fake-gist" id="fake-gist-115368"><code> use Moose; has fun => ( isa => "Constant" ); </code></pre>
My script iterates all the elements of the class fake-gist, wraps them with the same styling as the gists, and then fetches the actual gist with syntax highlighting. When the gist has been fetched document.write is trapped and instead of appending the gist to the end of the document it calls a replaceWith on the <pre> tag.
This also makes the page load much faster, since the fetching of gists is no longer synchronous.
Feel free to download the script and get banned from Blogger yourselves. You'll also need to add github's embed.css and jQuery 1.2 or newer.