What was the very first Apple product?

Their first product was the Apple I computer, hand-built by Steve Wozniak and first demonstrated in 1976.

You'll find plenty of details about Apple's early years in this section of the Apple, Inc Wikipedia entry.

"The Apple I, Apple's first product. Sold as an assembled circuit board, it lacked basic features such as a keyboard, monitor, and case. The owner of this unit added a keyboard and a wooden case."

From Wikipedia: http://en.wikipedia.org/wiki/Apple_I

The above picture is from April 24, 1984 at the flamboyant "Apple II Forever" introduction of the Apple IIc. This was shortly after the introduction of the Macintosh, so Apple wanted to assure dealers the Apple II would continue to be supported. The Apple II product line continued until the final Apple IIGS model was discontinued in December 1992. That's the Apple I at the bottom.