Yakpak is a children't user interface for OPAC data. It sits on top of a Z39.50 client. Produced by IndexData it is worth a look. It will be launched at ALA in Orlando.
Apparently they changed the name .. used to be called ChatMan. The old ChatMan demo seems to still be available:
http://www.indexdata.dk/chatman-eng/movie.php, if anyone's interested in seeing how the product's changed.