What they all do:
A. Analog Clock - 8-day spring-driven
B. Airspeed Indicator
C. Artificial Horizon (shows pitch and roll simultaneously)
D. Altimeter (shows feet above Mean Sea Level - MSL)
E. Turn Coordinator (shows rate of turn - and bank by inference -  and slip)
F. Directional Gyro (a gyroscopically-driven non-magnetic compass)
G. Vertical Speed Indicator (shows how fast you're climbing or descending)
H. Localizer/Glideslope Indicator (a navigation instrument that depicts position along a known line)
I. VOR Indicator (same as H, but without the glideslope indication)
J. 5 Engine gauges - Left Fuel Tank, Oil Temperature, Fuel Pressure, Oil Pressure, Right Fuel Tank
K. (there is no K, but it should be the Pitch Trim which is between the front seats on the floor and not shown in this picture)
L. Tachometer (engine and propeller speed)
M. Yoke (rotate to bank - ailerons, push/pull for up/down pitch - elevator)
N. GPS (Graphic map-style satellite navigation device)
O. Magneto Switch (like the ignition switch on a car)
P. Toe-Brake Pedals (these only work on the wheels, so only when you're on the ground)
Q. Rudder Pedals (control yaw left/right - rudder - they also steer the nosewheel on the ground)
R. Audio Panel-Radio Selector (to choose which of the radios are heard over the speaker or headphones)
S. Navigation/Communication Radio #1 (Nav side is depicted on H)
T. Radar Transponder (relays aircraft ID and Altitude information to ground-based radar sites)
U. Navigation/Communication Radio #2 (Nav side is depicted on I)
V. Throttle (push forward for fast)
W. Mixture Control (controls air/fuel mix - cars do this automatically)
X. Rudder Trim Knob
Y. Flap Handle - just out of sight - (lowers the wing flaps to help flying slow)
Z. Carburetor Heat Control (directs heated air into the carburetor to prevent/remove ice)
a. Ammeter (shows electrical load)
b. Automatic Direction Finder - ADF (shows bearing to AM radio broadcast beacons; we can listen to all the Cubs games on WGN and many small airports have a very small AM transmitter on the field to help in locating the airport)
c. Intercom Volume Control (when using headsets, this is used for the pilot and passengers to talk to each other)
d. Vacuum Gauge (the gyroscopic instruments are air driven and this shows how much suction the vacuum pump is producing)
e. Headset Receptacles  (a similar set is on the left side near f)
f. "Wing Leveler" Autopilot (this will automatically keep the wings level in flight without input from the pilot - very helpful when reading a map)
g. Magnetic Compass (the only instrument in the plane that is independent of any power source)