Hmm...
I looked at this question in two ways:
1) What brought Apple out from the "dark ages"
and
2) What brought Apple into the forefront and into its current sales boom?
To answer that question, I naturally turned to the iMac first. What a revolutionary computer that was.

Arguably the hallmark of '90s style and the epitome of how far the personal computer had come (not to mention a leader as it forged ahead with new technology and abandoned the old floppy drive), the iMac helps answer #1, but it doesn't fully answer it.
I think what really brought Apple out from the "dark ages" was a concerted effort at being more cautious with markets and how to enter them. As a result, Apple's product line became gradually more refined and the products Apple put out became even better (and leagues ahead of most PC competitors).
Now that brings us to #2: why the explosion in popularity?
I think this question is usually answered with "iPod." However, I have problems with such a simple answer. Granted the iPod is one of the most popular consumer products out there, but I have a hard time believing it is the sole reason people would "switch." An iPod is eye-catching and certainly allows people to say, "hey, they also make computers," but I don't think it's enough to get people to
buy computers.
Which brings me to what I chose in the poll: Intel Macs. Now I certainly believe that the "halo" effect was in force before the Intel switch, but I believe it really caught fire during the summer of 2005. With the Megahertz Myth no longer a problem, I believe it became easier for prospective buyers that may have once said "hey, they also make computers," to change that phrase to, "hey, I should
buy one of their computers."
I think that really explains the story of Apple's recent explosive growth. With Macs now able to compete directly against PC competitors, it becomes easier for buyers to say, "I want to buy a Mac," and once that happens, sales simply explode (as they have in the past few years).