How to fix a chipped countertop
As Isherwood said super glue is a great option if you have the whole piece to put back in place. If the piece is lost or doesn't completely fit you may want to consider replacing a segment of the countertop.

When retailers make cuts from countertop materials there is often small pieces left over. Ask at your local hardware provider or better yet at the location you purchased your countertops. With a steady hand you can cut a straight line in the least visible area and replace the entire area.