ross: "Blogware, the coolest tool since...the bread slicer". The "greatest thing sinced sliced bread" cliché is a well-worn one, and, necessarily, was subject to a Simpsons gag.

This is when Abe Simpson was talking about how the Simpson family first came to America:

Abe: The story of the Simpson family began in the Old Country. I forget which one exactly. My dad would drone on and on about America. He thought it was the greatest thing since sliced bread, sliced bread having been invented the previous winter.
Abe's dad: [holds up an America pamphlet] See that, son? That's where we're going to live. Maybe not today, maybe not tomorrow, but someday.
Abe: Later that day, we set sail for America.