The event will begin on 10am PDT at the Apple Town Hall in Cupertino, California.  As customary, expect the online Apple Store to be offline during the event.

iMac
Rumors point to the possibility that Apple will eliminate the low end 17" model and replace all other models with a redesigned brushed aluminum enclosure and keyboard.  If true, this would result in an overall increase in price for the low end iMac but should be offset thanks to the new design, performance, features, and capabilities.  The last iMac update occurred in September 2006, over 330 days ago.

.Mac
Apple is informing .Mac users that the service site will be undergoing maintenance on August 7th between 10am and 12pm PDT, the exact time of the Apple Media Event.  The message:

"Due to scheduled maintenance, .Mac members might be intermittently unable to access some .Mac services from 10am to 12pm PDT on 08/07/2007. We apologize for any inconvenience."

Many have taken the position over the past year that an update to the service is long overdue.  If updated during the event, Apple will position the service to Mac OS X Leopard ready prior Leopard's release in October.  Apple CEO Steve Jobs hinted that the service may see an update at the May 2007 All Things Digital Conference.

New MacBook Pro model?
The MacBook Pro line currently consists of 15.4-inch and 17-models.  Ever since the introduction of the MacBook Pro, many have complained about the lack of a smaller form factor to replace the now end-of-life 12-inch PowerBook.  If Apple introduces a smaller version of the MacBook Pro, I expect them to ensure that it will not cannibalize sales of the MacBook.