Apple (AAPL) has summoned the tech press to CEO Steve Jobs’s fortress of solitude, the company’s headquarters in Cupertino, for an unspecified product announcement. Those of us who have been covering Apple for a while know the drill – generally speaking, Jobs has three stages for product splashes: Macworld, the Worldwide Developer Conference, and home base.

The big conference announcements are orchestrated extravaganzas, but don’t dismiss home base for announcement quality – after all, the iPod itself was unveiled in the room Jobs has set aside for tomorrow’s festivities. (Apple also unveiled the iPod nano, the iMac G5 and the Power Mac G5 in late summer.) This time around, the word is that the gathering will be about Apple’s core computer business, not its iPod and iPhone lines.

So what’s in store?

I don’t know – which is part of the reason I’m eager to head over to the Apple campus and find out. But based on Apple’s track record in late summer announcements, I have a list of a few things I wouldn’t be surprised to see Jobs unveil.

1. An early (sort of) Leopard. Apple has said recently that Leopard, its major update to Mac OS X, would arrive in October. Leopard was originally to appear earlier this year, but the company shifted software resources to the iPhone to get it done and shipped by the June 29 deadline. Now that it’s clear that the iPhone launch was a success, and that Apple’s software talent doesn’t have to scramble to make dozens of critical fixes, I wouldn’t be surprised to hear that Leopard will ship a month or more earlier than the October date. Why does this matter? Software is a very profitable segment for Apple, and since the company has already projected that its margins will suffer this quarter, Apple’s balance sheet could clearly use the help.

2. New iMacs. There’s a lot of buzz about the possibility that Apple will refresh the iMac line with thinner machines with 20-inch and 24-inch screens, and faster Intel (INTC) processors. I would add to that the likelihood that the company will soon add LED backlighting to the flat-panel displays. LEDs provide two easy-to-grasp benefits: They consume less power, and they turn on faster. Apple already uses them in some MacBooks.

3. Wireless USB. Aside from the low-end and international sales, the broader desktop computer market has been weak lately. My hunch as to why: There aren’t enough compelling reasons to upgrade. Microsoft’s (MSFT) Windows Vista hasn’t captured the imagination of consumers, and unless you’re a gamer, there isn’t much software these days that requires dramatically faster computers. There is one thing, though, that I believe could capture people’s imagination: A clutter-free desktop area. Using new wireless USB technology, Apple could pull that off.

4. Hybrid hard drives. Dell (DELL) recently put them in its Alienware laptops. Seagate (STX) CEO Bill Watkins says they will be somewhat standard fare in laptops within a few years. They are hybrid hard drives, storage devices that combine the high capacity of hard disks with the speed of NAND flash memory. [CLARIFICATION: A V.P. at Apple reminds me that flash actually isn’t that fast, it’s just good at keeping data at the ready. I should have used more accurate language here. Thanks, Joz.] Using this type of drive, Apple could offer Macs that turn on and boot up just about as quickly as they wake from sleep now. Combined with the LED displays I mentioned above, that would be a nice energy conservation story.

5. HD optical drives. Apple certainly wouldn’t be the first computer maker to offer HD DVD or Blu-ray drives in its computers; Hewlett-Packard (HPQ) has offered a laptop with HD DVD for several months, and Blu-ray is showing up in ever more PCs. Apple has indicated in the past that it’s in the Blu-ray camp; it would be a shock if the company switched teams. If Apple does add Blu-ray to Macs, it would probably be to the Mac Pro; but frankly I think it would be a mistake to do this now. Consumers are still puzzled by the high-definition format war, and the winner won’t truly begin to emerge until this holiday buying season has played out.

6. New high-end displays. Apple has a 30-inch HD display ($1,800), a 23-inch HD ($900), and a 20-inch ($600). That lineup has gotten a bit stale. Is it time to amp things up? This could be an ideal time. Consumers will have flat screens on the brain this holiday season, along with Apple’s iPhone. You know what else might not be a bad idea? Apple could slap its slow-selling Apple TV box (Jobs calls it a hobby) on the back of an HD display, add a couple of I/O components, and presto – there’s a version of Apple TV that includes an actual television.

Whatever’s up Apple’s sleeve, here’s something to keep in mind: The events on Apple’s campus tend to be smaller affairs where Apple can demonstrate a new technology or design, and actually put it in the hands of the press. This is a venue where Apple likes to gather the tech influencers, convince them of a new idea, and send them forth to inform the masses.