One dæmon you probably won't need to reconfigure but still should be aware of is klogd, Linux's kernel log dæmon. This dæmon is started automatically at boot time by the same script that starts the general system logger (probably /etc/init.d/syslogd or /etc/init.d/sysklogd, depending on which Linux distribution you use).
By default, klogd directs log messages from the kernel to the system logger, which is why most people don't need to worry about klogd. You can control the handling of kernel messages by editing the configuration file for syslogd.
klogd can be invoked as a standalone logger; that is, it can send kernel messages directly to consoles and/or a log file. In addition, if it already isn't running as a dæmon, klogd can be used to dump the contents of the kernel log buffers (i.e., the most recent kernel messages) to a file or to the screen. These applications of klogd are useful especially to kernel developers.
For most of us, it's enough to know that for normal system operations klogd can be safely left alone (that is, left with default settings and startup options—not disabled). Just remember that when you use syslog in Linux, all kernel messages are handled by klogd first.