What medical equipment is usually found in an ambulance?

ok well here is a short list:

stretcher
oxygen tanks
tubing
masks
bandages of all sizes 5x9, 4x4, rolls, bandaide
triangle bandages
air or foam splints
tape
mass trousers
ambu bags
stethoscope
Blood pressure cuffs in varied sizes
towels
blankets
sheets
gloves (lots of them in differnt sizes)
sharps box
glucometer
gluco tubes
alcohol wipes
saline solution
hare traction splint
spine boards
cpr board
AED (if certified depending on the state)
head blocks/chucks
straps
radio

i know i forgot stuff - there is sooooo much

IV ?

Everything you would find in an ICU room or any room with a
patient who has had a cardiac/respiratory arrest.

IV's, suction for mouth-nose-stomach, defibrillator, heart
monitor, oxygen, tubes for airway & stomach, emergency drugs esp for heart & blood pressure. Stethoscopes, blood pressure cuffs, etc.

There isn't enough space to answer with a list of all the equipment, but these are the categories of equipment that are on an ambulance as far as for EMTs.
patient infection control, comfort, and protection supplies, initial and focused assessment equipment, equipment for transfer of the patient, equipment for airway maintenance, ventilation, and resusciation, oxygen therapy and suction equipment, equipment for assisting with cardiac resuscitation, supplies and equipment for immobilization of suspected bone injuries, supplies for wound care and treatment of shock, supplies for childbirth, supplies, equipment, and medications for the treatment of acute poisoning, snakebite, chemical burns, and diabetic emergencies, medical equipment for paramedics and physicians, and safety and miscellaneous equipment.
I used to be an EMT myself, and hope to retain some day again.

"Me" had a great answer but it also depends on what state and county you're located in due to protocols. It also depends on if the rig is being run by EMTs or Paramedics, privately run, county or state run. There are some things that an EMT rig may not stock because it would be out of protocol for the EMT to use such as medications and other instrumentation used for invasive procedures.

everything you need to sustain life.

stretcher
oxygen tanks
tubing
masks
bandages of all sizes
triangle bandages
air or foam splints
tape
mass trousers
ambu bags
stethoscope
Blood pressure cuffs in varied sizes
towels
blankets
sheets
gloves (lots of them in differnt sizes)
sharps box
glucometer
gluco tubes
alcohol wipes
saline solution
hare traction splint
spine boards
cpr board
AED (if certified depending on the state)
head blocks/chucks
straps
radio
anesthesia
and seat for the patients relatives
and a driver and helper

responder bag (w/ intubation set and IV set)
portable oxygen supply with portable ventilator
defibrillator
cervical collar
foam splint or vacuum splint
portable suction machine
ACLS drugs

these are the foremost things an EMT need to attend to a patient immediately, then the rest of the equipments from the ambulance will follow, such as the stretcher, traction, spine board, scoop stretcher, etc.

Medical equipment??? we don't carry medical equipment. Kidding of course.
KEDS
CIDS
Backboards
Prosplints
scoops
oxygen
medical air
suction equipment
iv supplies
defibrilators
Monitors
c collars
2X2's
4X4's
5X9's
traukma pads
burn sheets
ob kit
cot
urinals
vomit buckets
bedpans
BVMs
NC
NRB
intubation equipment
saline
MAST Pants

Take an EMT course, it'll be easier than listing everthing in an ambulance. And you'll actually know what I'm talking about :-)