Actually, the reason that clock speeds aren't doubling and being shouted from the rooftops anymore is that clockspeed can no longer be taken as an accurate measure of a processor's abilities.
Chipmakers are more concerned with caching and other efficiency issues. Furthermore, the industry is slowly making the shift from 32-bit to 64-bit processors. Processors are also now being optimized for threads, but this is not to be confused with "Hyperthreading".
Hyperthreading is a so-called 'feature' on some more recent Intel chips which has received rather poor reviews across the board. I've actually seen a review or two which reported performance worsening significantly with hyperthreading enabled.
Multiple processors are nothing new in the server world, and aren't really headed for desktops anytime soon. What you may be thinking of is double-core processors, which is a sort of similar idea. Double cores allow concurrent execution of threads - which means threaded applications or multi-tasking scenarios will see a major performance boost.
So what is 'threading'? Well, here's the real short & sweet version:
Think of threads as 'threads of control'. Now think of a program as a braid of threads. Different threads go into different places, and play different roles in the overall pattern of the braid.
Here's a simple (but not very realistic) example of a music player:
One thread might be reading some data from your CD, and another thread might take that data, play with it a little, adjust volume, bass, and treble, and another thread pipes it out to your speakers.
With one 'core', each thread has to take a turn at being run. One thread goes for a little while, then it stops and the next one goes for a little while, and the it stops and the next one can go for a little while... etc.
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With two cores, two threads can be working at once. Not only do you get more done at once, but the guys who are in line to get their turn don't have to wait quite so long.
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Anyway, I can talk your ear off on this subject (I've done a few courses about these things now), but hopefully that's understandable even to those who aren't Superman with a computer.