Antenna House XSL Formatter: XSL formatting engine that conforms to XSL W3C recommendation. [Commercial]
Big Faceless Report Generator: Java Report Writer to convert XML to PDF. Creates dynamic reports with JSPs and Servlets. Features include encryption, bar codes, graphs and charts, custom fonts, Unicode support. [Commercial w/ Evaluation]
FOP: XSL-FO to PDF converter. A part of Apache's XML project [Open Source, BSD-like].
XEP: XSL-FO to print (PDF or PostScript) converter written in Java. [Commercial]
Xinc: A Java XSL-FO viewer and PDF generator.