OK, RISC OS Pi squeak is now available as a tentative demo pre-alpha possibly useful maybe release at http://www.rowledge.org/tim/squeak/Squeak3-9-RISCOS.zip 
If you try it and like it, remember to mentally thank Chris Cunnington for providing the dev-tools and the Pi Foundation for providing the tasty Pi. And offer up wishes for somebody realising that they need to *pay me* to develop stuff.

Apparently Scratch runs on it, though I haven't tried and wouldn't really have any current experience to judge it by.

tim
--
tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
Life would be much easier if I had the source code.