You can download the latest release version from the distribution directory.
Each version exists as binary (bin) and source (src) distribution. The binary distribution contains the compiled package along with the documentation (including some example XSL-FO files). The source distribution additionally contains the whole source code.
If you want to work with the latest and nicest code, you can download it from CVS. See the section on AnonCVS in the xml.apache.org documentation for details.
Sometimes people have difficulties to access the CVS server; in this case you can download a snapshot from the CVS files here. Please be aware that the snapshots currently mirrors the development code for the upcoming FOP 1.0 and not the code from the current releases. You need to download from CVS in this case. (See the note below)
If you don't download a binary distribution you have to build FOP yourself - see Compiling FOP for details.
To run FOP from the command line, see Running FOP.
If you are interested in embedding FOP in a Java application of your own, see Embedding FOP.