Unobtrusive Sidenotes: They look like pullquotes, but they’re actually tied to a highlighted block of text in the main body.
We are of the belief that footnotes — at least the ones worth reading — suck. They suck because they are elsewhere, usually far away from the line-of-sight we’re focused on when we read. It would be nice to be able to optionally just glance over and take that brief little detour if we so choose. It’s footnotes on steroids: sidenotes.
There’s an example here. It’s very nicely done.