When I started exploring XSL-FO processors, I wanted to look at all the 
available tools (both open-source and commericial). However, I couldn't 
find a list of all available processors. The few lists I came across 
were not recently updated. Here is the list I came up with. Hope this 
helps.
 
http://rkamal.blogspot.com/2004/12/list-of-xsl-fo-processors.html
 
- Kamal