A little over two years ago, Steve Jobs described Apple as being in three businesses and a hobby. That was a broad-brush, hardware-centric description of what Apple was up to at the time. Even then there was more going on at Apple than fit under the umbrella of that description, and that's certainly become more the case since.
First consider the hardware lines...
1) Mac mini, MacBook, MacBook Pro, iMac, and Mac Pro
2) AirPort Express, AirPort Extreme, and Time Capsule
3) iPod shuffle, iPod nano, and iPod classic
4) Apple TV
5) iPod Touch and iPhone
...soon to be joined by a new family of tablet computers,
and the consumer (non-pro) software...
1) iLife and the apps included with Mac OS X, like Safari
3) Bento (from FileMaker, a subsidiary)
then consider the cloud services...
1) MobileMe (the predecessors of which were .Mac and iTools)
2) iTunes Store (now including the App Store)
Even this isn't a comprehensive view, as it neglects the pro apps, accessories, AppleCare, paid training, and on and on.
Apple isn't in just three businesses, but dozens, most of which produce at least modest revenue streams, and into the future, despite continuing focus on and healthy growth of hardware overall, the proportion of total revenue made up by non-hardware businesses is likely to grow.
I say this partly because the signs point to Apple putting increasing emphasis on the cloud, and partly because, aside from the iTunes Store which is about content and software delivery, they have yet to have a runaway hit there. MobileMe (like its predecessor .Mac) is successful in the sense that it produces a revenue stream, but the numbers pale in comparison with free services from Google, Yahoo!, and others, and pundits disagree as to whether it's worth the price to the consumer.
While the free services make their money from advertising and look for ways of differentiating premium versions, Apple has and will continue to focus on making theirs useful, easy to use, fast, secure, and elegant. While the others increasingly rely upon dedicated clients, particular browsers, or plug-ins, Apple's services, including the iTunes Store for content not requiring DRM, will be moving toward working with any platform that supports web standards.
Given Apple's penchant for excellent execution, sooner or later their cloud services are sure to stand out as being worth paying for while the vast majority of others won't be. And while those services will work with any platform supporting web standards, given Apple's penchant for integration, there will always be some advantage to using their hardware and software with them, making them even more compelling for those already using a Mac, iPhone, or Apple tablet.
This is a strategy that can only pay off in the long term, but one that will also surely do so.