Each of the file system projects described above maintains its own home page where you can find mailing list information as well as further documentation and FAQs.
http://e2fsprogs.sourceforge.net/
http://www.zipworld.com.au/~akpm/linux/ext3/
http://www.namesys.com/
http://oss.software.ibm.com/developerworks/opensource/jfs/
http://oss.sgi.com/projects/xfs/
A comprehensive multipart tutorial about Linux file systems can be found at IBM developerWorks: http://www-106.ibm.com/developerworks/library/l-fs.html
For a comparison of the different journaling file systems in Linux, look at Juan I. Santos Florido's article at Linuxgazette: http://www.linuxgazette.com/issue55/florido.html.
Those interested in an in-depth analysis of LFS in Linux should try Andreas Jaeger's LFS site: http://www.suse.de/~aj/linux_lfs.html.