The XML Apache Project has posted version 0.92 of FOP, an open source XSL Formatting Objects to PDF/PostScript/RTF converter written in Java. "This third release contains many bug fix release and new features compared to 0.91beta." Java 1.3 or later is required.
FOP's improving, and it's good enough for simple protoyping and experimenting. However it's still not close to ready for most serious production needs. There are just too many missing pieces. The most important ones for my needs are automatic table layout, floating images, and whitespace preservation in code samples. Hopefully these will be improved in future releases in the push to 1.0.