Any time Apple's CEO, Steve Jobs, gets up and makes a keynote address at an Apple event, hordes of Mac users go totally bonkers speculating about what new products will be announced. The keynote address is often referred to as the "Stevenote," though for some people, just saying the word "keynote" is enough to get them a little excited.
The most prominent "Stevenote" of the year takes place in the first half of January, at the MacWorld San Francisco expo. Other notable Stevenotes occur at MacWorld Paris (which involves staying up until 3 or 4 AM to hear what Steve has to say), the Worldwide Developer's Conference, and various special events throughout the year.
I was thinking of buying a new PowerBook, but I have to wait until after the Stevenote in case they announce new ones!