NOTE
**Current theory is that Superman's abilities and powers are psionic in origin. Thus, this set-up of his powers will use that assumtion to explain his powers. It is also assumed that this ability is fueled by the earth's yellow sun.**
PHOTOKENESIS
Superman's main source of energy and power is from the yellow sun which warms the earth. In essence, Superman is a solar battery of immense proportions. Thus, in the absense of a yellow sun, his powers will eventually fade and decrease, to the point that he can become comepletely mortal.
IMMUNE SYSTEM
Basically, Superman's immune system and metabolism moves at such a great rate that no natural earthly toxin has a chance in his system. It also allows him to heal at an incredibly remarkable rate. As long as he is in the light of a yellow sun, even the worst of wounds will heal quickly. That is, /if/ he has not been seriously exerting himself.
INVULNERABILITY
Superman's body is able to take incredible amounts of pressure, strain, and such. He can survive in the vacuum of space, the fires of a forge, and worse. It is thought that this is due to an automatic, telekenetic 'shield' of sorts that surrounds his body, as well as whatever he's wearing. This shield extends approxamately one centimeter from his body, thus explaining why his suit is less likely to be torn, while his cape often gets shredded. This field can protect Superman from the deadliest of man-made weapons, and even blows from some of the universe's most powerful beings. However, being that such energy runs on a 'battery' of sorts, it is feasable that after a while, even this can run out. This may explain why Doomsday was eventually able to kill Superman.
SUPER SPEED
Using his telekenetic powers, Superman can propell himself at incredible speeds. On the ground, or using only his limbs, the differential of speed from his super-flight would only be noticeable to other speedsters. He has been clocked against the current (3rd) Flash in his world (who was last clocked at 186,000 miles/second), and came in only slightly slower...(this was in flight -- and he was severely drained afterward). His reaction time is somewhere near 1000 times that of a regular human.
SPEED THINKING
Superman thinks at a rate that is remarkably faster (1500 times) than even the most ingenious humans. This allows him to process all he sees, even when at high-speeds of flight or movement. This also allows for excellent speed-reading, and a photographic memory.
SUPER FLIGHT
This is similar to the above. However, this allows him to defy the natural laws of gravity and to move at speeds almost rivaling the most recent Flash (again, nearly 186,000/miles per second...although this is absolute max, and is incredibly draining). He cannot keep up either of these speed idefinitely, however, and must eventually stop. However, the likelyhood of him reaching said point is highly unlikely in normal RP.
SUPER HEARING
Superman's hearing is advanced to such an incredible rate that he can even hear a number of radio frequencies, specifically honing in on police and medical bands. It is even joked that he could hear a pin drop during a White Zombie concert, if he focused. Thus, he can hear things from many miles away. However, this does make him slightly vulnerable to high-frequency sounds.
SUPER BREATH
Superman's lungs have advanced to such a level that he can emit gale-force winds with his breath (although it is no effort for him to alter the level ofthis strength), or to emit a cold wind from his mouth cold enough to freeze water instantly.
SUPER STRENGTH
Superman has strength which is unparalleled, as far as he has encountered. Only two villains, Savior and Doomsday, have come close to him in strength. This is mostly accomplished by his use of telekenetics, lowering the weight of an object. However, this is transferred through touch ONLY. For the sake of providing limits (although none have truly been stated or found), Superman could, with much strain, lift approximately 650 tons. However, such a move would require direct exposure to the sun's rays, as he would deplete his stores quickly. He can regulate how much force and strength he uses, and often does so when going against an opponent, seeing what they can handle without killing them
SUPER VISIONS
The source of this particular power is still debated. However, it allows him the following ranges of vision:
-X-ray (ability to see through almost all objects...except lead)
-Heat-vision (these beams of light are so hot that they have been used, at MAXIMUM intensity, to ignite dead stars -- and this really drained him. Thus, this can easily burn through the majority of earth materials. He will rarely use it against an enemy unless it is obvious that nothing else will do the job)
-Telescopic vision (Superman can see for hundreds of miles in a straight line)
-Infrared vision (This is basically night vision)
-Microscopic Vision (The ability to see objects on a microscopic scale)