http://www.tldp.org/HOWTO/Filesystems-HOWTO.html Always the place to begin. The file systems HOWTO.
http://en.wikipedia.org/wiki/Filesystem Wikipedia on how file systems work in various operating systems.
http://en.wikipedia.org/wiki/Comparison_of_file_systems Helpful chart on differences between file systems, with links to the Wikipedia articles on each file system.
http://www.namesys.com The group in charge of ReiserFS.
http://batleth.sapienti-sat.org/projects/FAQs/ext3-faq.html The Linux ext3 FAQ list. Differences between ext2 and ext3, as well as troubleshooting problems.
http://oss.sgi.com/projects/xfs The XFS for Linux site.
http://www-106.ibm.com/developerworks/linux/library/l-fs9.html An IBM DeveloperWorks article on XFS.
http://www-106.ibm.com/developerworks/edu/os-dw-linuxjfs-i.html A JFS tutorial; free registration with DeveloperWorks required.
http://sources.redhat.com/lvm2 The Logical Volume Manager home page.
http://www.tldp.org/HOWTO/LVM-HOWTO The LVM HOWTO page. Should have information on LVM2 by now.
http://usalug.org/phpBB2/viewtopic.php?p=33142 Tuning up IDE hard drives with hdparm. A useful tutorial.
http://www.gnu.org/software/parted The GNU Parted home page.
http://www.freeos.com/articles/3921 A basic introduction to the Logical Volume Manager. Includes command-line instructions for building logical volumes.