Yes, from my web-centric point of view the tryruby model is very interesting. I find the idea of HTML literals quite interesting as well; e.g., instead of just repr(obj), an object can have a rich HTML representation. If you combine that with a clean callback technique and higher-level HTML widgets, you could even make an Ajax application interactively composable -- and throw in some automatic persistance to boot, and you have a persistent image/IDE. This is Yet Another Idea that I want to pursue, of course ;) A scratchpad of objects could address some of the issues of combining a linear narrative (like a tutorial) with the freedom of an interactive prompt.
And, as I think about it, that would totally be Hypercard. Tasty.