This has got to be the best name in the bible, purely because it is the longest name in there which I can pronounce. As has been mentioned, it was the name of a son of the prophet Isaiah and previous to his birth it was a message Isaiah was commanded to write on a large tablet (maybe a giant asprin or something). These two occurences were supposed to serve as prophetic signs to the people of Judah, the southern Israelite kingdom which was formed when two of the twelve tribes of Israel split away from the other ten, who went on to form the northern kingdom.
The situation at the time saw Judah being threatened by the combined armies of Israel and Syria who's kings, Pekah and Rezin respectively, had allied in an effort to destroy Judah. Judah's king, Ahaz, was getting a tad worried about this, especially as the armies were encamped a mere two days march away from them. Fearing his imminent defeat, he bribed the king of Assyria for military support.
Isaiah was to prophesy the outcome by making these two signs, first by writing the words "maher-shalal-hash-baz" on a tablet and then naming his newborn son the same. The word itself means something to the effect of "Hurrying to the spoil, he has made haste to the plunder" which, as Isaiah himself explained, meant that Assyria would come and utterly destroy the two enemies of Judah. In chapter 7 and verses 16 - 17 he says:
The land that thou abhorrest shall be forsaken of both her kings. The LORD shall bring upon thee, and upon thy people, and upon thy father's house, days that have not come, from the day that Ephraim departed from Judah; even the king of Assyria.
As it turned out, he was right. The Assyrian king Tiglath-pileser III invaded Israel and captured many of its cities, plundering the land and taking a number of inhabitants into captivity in the process, after which the Israelite king Pekah was put to death. The Assyrians then saw to it that a similar fate awaited Syria; they captured its capital Damascus, took its people into exile, and executed the Syrian king Rezin until he died.