Rumors of a sub-notebook version of the MacBook Pro have been circulating for some time, but now coming on stronger than before leading up to Macworld Expo 2008. As always, the rumors include a long list of features and the requisite mockups and blurry digital images.

AppleInsider and MacRumors, both Apple-related rumor Web sites, offer up details about the phantom laptop that many speculate really will make an appearance during the Macworld Expo Steve Jobs keynote on January 15. Features include an ultra-thin design, a 13-inch display, a multi-touch trackpad, NAND Flash memory, and an external optical drive.

A slightly out of focus image of what appears to be a redesigned -- and substantially smaller -- MacBook appeared on the MacRumors forums, which will likely add to the speculation over what Mr. Jobs will announce at Macworld Expo.

MacBook Ultra-light image from MacRumors

Popular Mechanics took a more speculative approach and created an animated mockup of what a new portable tablet-style Mac could look like. The "MacBook Plus" includes a removable touch sensitive display and external optical drive, and switches between Desktop and iPhone-style interfaces.

PM mocks up a Mac laptop/tablet hybrid.

With the eyes of the media, investors, and fans clearly focused on Apple during Macworld Expo 2008, thereis a good chance Mr. Jobs will unveil a new and exciting product. Weill have to wait, however, until his keynote presentation to see if it is the fabled ultra-portable Mac.