Hi Ellen - a one block wonder is a quilt made from one block but it has come to mean the kaleidoscope deisgns from the technique developed by Maxine Rosenthal. There's a Topic List here on the board where you can see one block wonder tops and quilts and read all about them! Also the topic heading explains the differences between one block wonders (OBWs), stack n whack and other forms of kaleidoscopes. Hope this helps. The OBWs seem to be rather a craze on here at the moment.
http://www.quiltingboard.com/virtual_section_list.jsp Scroll about half way down the list.