The modern alphabet...
English uses what we call the Latin (or Roman) alphabet. This alphabet, with minor variations, is used throughout most of Western Europe and the Americas, and also in far-flung locales like Vietnam and Malaysia.
The Latin alphabet dates back to at least the 7th century B.C., and was the result of evolution, not invention. It was adapted from the Etruscan alphabet, which was itself an adaptation of the ancient Greek alphabet. The Greek alphabet, in turn, was a direct descendant of the Phoenician alphabet, which was taken from hieroglyphics. The Phoenician alphabet already had a fixed letter order, which was generally retained by the alphabets it inspired.
The earliest Latin alphabet had only 21 letters, in the following order:
A B C D E F Z H I K L M N O P Q R S T V X
This looks pretty normal except for the five missing letters, and the early appearance of Z. (The Greek zeta has a similar position.)
The Romans soon realized that their language had no use for the Z (pronounced /dz/ by the Etruscans, a sound that did not occur in Latin) and dropped it.
Conversely, Latin required a /g/ sound, which did not exist in Etruscan. Around the 3rd century B.C., this deficiency was addressed by adding a new letter. The Romans had been using C for both /c/ and /g/, and the new G was nothing more than a C with a bar added to it. Instead of putting the new letter at the end of the alphabet (or after the C from which it was derived), it was placed in the spot abandoned by the Z.
A hundred or so years later, when the empire was at its peak, the Romans realized they needed more letters. They had conquered the lands of Greek-speaking people, and more and more Greek words were entering Latin. So the letters Y and Z (upsilon and zeta) were added (or added back) to the Latin alphabet. These two letters were placed at the end of the alphabet, since there were no "empty" spots anywhere else. The new 23-letter alphabet looked like this:
A B C D E F G H I K L M N O P Q R S T V X Y Z
It would be more than a thousand years before the alphabet changed again.
As we learned in Indiana Jones and the Last Crusade, the letters I and V were used as both vowels and consonants until the Middle Ages (I was used for /i/ and /j/, V for /u/ and /v/). This seemed needlessly complicated, so the letters J and U — slight stylistic variations of I and V that were already being used by many scribes — were added to the alphabet. They took their places right next to their cousins, with the vowels in both cases coming first.
The last letter to be added was the W. This unwieldy letter was originally written, as its name suggests, as nothing more than a UU (or VV ... "double 'V' as it's pronounced in Russian ... and other Cyrillic languages). Naturally, it took its place after the U/V pair. With W firmly established, our modern English alphabet was complete:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
So we know, more or less, why G, Y, Z, J, V and W appear where they do. But what about the rest? The order was simply passed down from the Phoenicians (and possibly even from farther back). Some linguists speculate that something about the order made it easy to remember. It could also be that the symbols were somehow ranked in order of "value" — perhaps all the letters had numerical or astrological equivalents.
Or maybe the Phoenicians just liked the way they fit in their alphabet song.
http://www.cedarland.org/alpha.html