Steel
Graphite
Titanium
Stiffness
Frequency
Torque
Kickpoints

Steel
Steel shafts are generally made from carbon steel or occasionally from stainless steel. For the most part, the manufacturing process between the two are similar. A steel strip is rolled into a tube, and is drawn over a mandrel until the diameter and wall thickness are reduced to their exact specifications. At this point the step pattern is formed on the shaft. Then the walls are made thinner at the grip and thicker at the tip to give the shaft its flex characteristics. Then it is hardened, tempered, straightened and stress relieved. The final step is to polish and chrome plate the shaft. One of the best features of the steel shaft is the ability to have the same "feel" throughout the entire set. This means that the stiffness in the 3 iron will will be the same as the 9 iron. Other features are its durability and price.

Graphite
Graphite shafts are made from a graphite tape. The tape, which has an epoxy binder, is wrapped around a steel mandrel. The wrapped shaft is then temperature cured and the mandrel removed. The raw shaft is then sanded and cut to proper length, at which point it receives a clear or colored paint coating. Its most talked about feature is its light weight. It also helps dampen the vibration caused by clubhead impact with the ground. A few of the drawbacks are the "feel" of the shaft (some people complain that a stiff graphite shaft does not feel like a stiff steel shaft), the stiffness may not be consistent throughout a set, and its price tag. A new manufacturing process called "filament winding" can produce a set with more consistency, but at a higher price.

Titanium
I have very little information regarding the titanium shaft and its manufacturing process. Among some of its features are its weight (lighter than steel), and its vibration dampening. Some complaints are that the shafts are too stiff, and it carries a big price.

Stiffness
The stiffness, flex, or deflection of a shaft defines the bending characteristics of the tube, when a load is applied to the shaft. The most common shaft flexes are designated as X (extra-stiff), S (stiff), R (regular), A (man's flexible), or L (ladies'). For people with high swing speeds, it's desirable to have a stiffer shaft to keep the club head from lagging behind. For people with slower swing speeds, the more flexible shafts offer an extra "kick" at the bottom of the downswing to help propel the ball.

Frequency
Some shafts are rated for "frequency", an alternative way to express stiffness.The "frequency" indicates how how fast a "standard" club would vibrate if made with that shaft. The stiffer the shaft, the faster it will vibrate. A rough guide to translate between frequency and traditional stiffness ratings is:

Frequency (cycles / minute) Stiffness (grade)
< 240 L
245 A
255 R
265 S
> 270 X

Torque
Generally torque is a rating applied to a graphite shaft. It specifies the "twisting" characteristics of the shaft. The normal torque rating of a steel shaft for woods is about 2.5 degrees, and 1.7 for the irons. The general range of torque ratings found on graphite shafts are from 3.5 to 5.5 degrees, although it is possible to get shafts with lower or higher ratings. The higher the torque rating, the more the shaft twists for a given twisting force. The torque rating also seems to be tied to the stiffness of a shaft. The lower the torque rating, the stiffer the shaft.

Kickpoints
The kickpoint, bendpoint, or flexpoint defines where the shaft will bend. It affects the trajectory of the shot; the higher the kickpoint, the lower the trajectory. The effect in trajectory is small but measurable. For someone that generally hits the ball with a high shot trajectory, a High kickpoint is desirable in a shaft. For someone with a low shot trajectory, a Low kickpoint helps get the ball airborne and on a higher flight path. The kickpoint also affects the "feel" of the shaft. A golfer who can feel the difference finds the high bend point makes the shaft feel like "one piece", while with the low bend point, the shaft feels as though the tip whips the clubhead through the ball.