Without going into terminal commands (From my point of view, less friendly way of inviting a new user to Ubuntu.. until he/she feels the force) like:
lshw - Shows you information about all hardware
lsusb - Shows you information about all USB hardware
lspci - Shows information about all PCI compatible hardware
cat /proc/cpuinfo - Shows detailed information about your CPU
dmidecode - Shows you information about hardware
And others like
hdparm that can give information about HDD and temperature readings.
Seeing as you are new, I will mention easy to use GUI tools that can quickly help you find important information about your PC:
Shows information about all type of storage devices, including but not limited to HDD, SDD, Flash Drives, External (Connected) USB Drives, etc..
To use it just open DASH (By pressing the SUPER key) and type
disk. You will then see the option "Disk Utility".
DISK USAGE ANALYZER
Very good program to analyze the (As the obvious name implies) disk usage. It can very useful when doing a cleanup on old files and such.
As with Disk Utility, type in dash
disk and the second option will be the "Disk Usage Analyzer"
Ubuntu Detail Information
Type in dash
detail and you will see a cog icon with the name "Details". It will show you basic information on your machine:
I should mention that if you are using an Nvidia card, you need to update Ubuntu 12.04 with the latest upgrades in order to see the Video card name.
Very nice program to see information about your computer.
It can be installed via the Software Center by looking for "Sysinfo" or "Hardware"
or clicking here
Very nice program based on LSHW to show you in a graphical way all the hardware. As the previous one I mentioned, it can also be installed from the Software Center by looking for "Hardware" or clicking here
So as you can see there are MANY programs to check for hardware and hardware information in general. I suggest playing with Software Center to find even more but this should be enough to know most if not everything about your computer.