What does Apple normally announce at events? Tomorrow (October 20th, 2010) Apple will announce something. 

What have they announced at previous Mac events and what are some of the things are "usual"?
This is an open ended question;

Traditionally Apple at events such as MacWorld, WWDC, etc. run down as follows:


Run down of current company progress showcasing how much Mac OS X has grown
New hardware updates with technical details and great product shots.
New software - whether it's upgrades or completely brand new products. Lots of demos.
Occasionally a one more thing, usually the biggest thing of the show if it occurs.