$ dmesg ⇒ Detected hardware and boot messages (dmesg many more options)
$ cat /proc/cpuinfo ⇒ CPU model
$ cat /proc/meminfo ⇒ Hardware memory
$ cat /proc/interrupts ⇒ Lists the number of interrupts per CPU per I/O device
$ lshw ⇒ Displays information on hardware configuration of the system
$ lsblk ⇒ Displays block device related information in Linux (sudo yum install util-linux-ng)
$ free -m ⇒ Used and free memory (-m for MB) (free command in detail)
$ lspci -tv ⇒ Show PCI devices (very useful to find vendor ids)
$ lsusb -tv ⇒ Show USB devices (read more lsusb options)
$ lshal ⇒ Show a list of all devices with their properties
$ dmidecode ⇒ Show hardware info from the BIOS
$ hdparm -i /dev/sda ⇒ # Show info about disk sda
$ hdparm -tT /dev/sda ⇒ # Do a read speed test on disk sda
$ badblocks -s /dev/sda ⇒ # Test for unreadable blocks on disk sda