It's worth prefacing this contribution with a warning. Much of what you are about to read is speculation, fuelled by nothing more than the bonfire of "he said", "she said", and "I heard in an internet chatroom" that is the Mac rumour mill in holiday season.

If anyone is discussing what Apple chief executive Steve Jobs will unveil in his new year keynote to the January MacExpo conference, only one thing's for sure: there are a few things we know for sure.

That doesn't stop the world of Mac fandom from speculating, and looking forward to today's show. Part of the reason they are so keen is that Jobs delivers his speech with the kind of panache and theatrical presentation that makes it worth watching. But the fans also love the fact there will always be a surprise.

Once, only once, the surprise was that there was no surprise. But mostly, despite the rumour mill's energy and impressive output, the gossips rarely get all the components of a Steve Jobs keynote spot on. And that's part of the fun.

Take last year, when Apple users approached the show with some gloom. As well as a sluggish economy, which was taking its toll on the entire technology sector, Apple itself was being talked down by supposedly in-the-know analysts and pundits. One US investment house even downgraded Apple stock to a "sell", berating the company for its "skimpy" product development line.

The analyst who penned that must have had a difficult day after Jobs took to the stage. Apple's CEO promised enough announcements for "two Macworlds", and promptly delivered two new laptops, a new web browser and revamps for a range of the company's digital media applications.

So what of this year? The smart money is on the iPod music player taking centre stage. There has been persistent talk of changes to Apple's hottest product for some time and, given its importance to Apple's reputation and bottom line (it's made Apple more relevant, and profitable), it seems to make sense that the company would want to keep the range fresh.

The gossips can't agree on what, exactly, will happen, however. Think Secret, a well-regarded gossip site, suggests Jobs' keynote will be "music centric". It reports with some conviction that Apple will launch new low-end mini iPods in a range of colours, "including stripes", with prices starting at a remarkably low $100 (£55) for a machine that could hold 400 songs. Audiorevolution.com correctly notes that such a device, which might use flash memory rather than a hard drive to store the music, would provide a major boost to Apple's iTunes Music Store.

Think Secret also predicts Apple will also offer coloured cases for the existing iPod range, and revamp its iLife digital media suite, which was launched at last year's show. The site has the distinction of being proved right on one prediction already. Its prediction of a new version of the video editing package, Final Cut Express, has already been fulfilled after copies were spotted at a US computer store by Macrumors.com spies.

But that vindication doesn't stop Apple Insider from boldly contradicting Think Secret's assertion that there will be no computer hardware announcements at the keynote. Apple Insider predicts new G5 desktops for professional Mac users and a long-awaited upgrade to Apple's XServe server. The latter prediction comes complete with more information than you'll likely want to know on problems with the new machine's self-diagnosis systems.

In its grand rumour roundup Macrumors.com notes Apple has trademarked the term iWrite, which has - no prizes for guessing - led to suggestions the company will continue its process of offering an alternative to popular Microsoft programs by unveiling a new word processor. Safari, a web browser, and Keynote, a rival to PowerPoint, are already produced by Apple.

And if all these rumours seem a little pragmatic, you could always turn to the more wild suggestions being offered in some quarters. The Register claimed in December that a new, cheaper iMac was being planned, despite the recent launch of a version of Apple's consumer desktop computer with a 20-inch screen. The site also speculates that the company will use the Mac's 20th anniversary to launch a "special" Mac; a tablet computer is their bet for what could be waiting in the wings for us tomorrow.

I'm not holding my breath. But, as experience tells us, you never know. With Apple's reputation for surprise innovations, you'd have to be rash to make any predictions.

· Neil McIntosh will post first details of Apple's announcements on Online's weblog, Onlineblog.com, from 8pm this evening. Fuller details will be on Guardian Unlimited tomorrow.