Asterisk
I didn't write Asterisk, the open source PBX. I did contribute a minor bit of code surrounding distinctive ring detection and the options for configuration thereof.
sysfs.pl
A long time ago, I created an admittedly ugly script to get information from the /sys filesystem on Linux about SCSI disks.
The script is particularly helpful for obtaining information on the raw size of SCSI disks, LUNs (in hex), and other such bits produced by the /sys filesystem. It's like udevinfo -a -p except not as good. But it prints the LUNs in hex which can be quite helpful. Download by clicking on the script name above. Use at your own risk.