Three of the top four Google hits for stretchtext currently point to Tinderbox projects. That’s interesting, because Tinderbox isn't particularly about stretchtext. But it's a popular tool for people who are interested in serious hypertext, and stretchtext is interesting to the same people.
And it’s really easy to build nice export support for stretch text (or other nifty Web tricks and widgets) in Tinderbox.
After these, there’s an interesting Hypertext '05 paper by Tor Brekke Skøtskift on using stretchtext in a mystery story. (I think mystery is going to be especially challenging for hypertext, but it’s always worth trying again.)