Here is a list of things I gathered over couple of years.
cat /proc/cpuinfo -- displays info about your processor
cat /proc/meminfo -- displays info about your memory
ls -al /proc/kcore -- to see how much ram is installed
df -h -- displays disk usage information
lspci -vv -- displays all devices connected to your PCI bus
lsusb
lshw
lshw-gtk
fdisk -l -- displays all disks/partitions that your computer knows about
free -m -- displays memory usage
/proc/ide -- to see the detected IDE drives
/proc/bus/scsi -- to see the identified scsi systems
/proc/sys/dev/cdrom/info -- to see capabilities of CD drives.
Please let me know if there is something else that could be included in this
list.