One way to minimize chipping when cutting melamine with a circular saw is to turn it over so that the good side is down, as that side will chip the least. On the top side, where the saw blade comes up through the panel, score your cut line deeply with a knife first and then cut just barely away from the score line. Any plastic that wants to lift up and chip will snap at the cut line, leaving a clean edge.
If you are using a jig saw, get yourself a "down cutting" jig saw blade. The teeth point down rather than up. This will chip on the bottom, but give you a clean cut on the top. The only caution is to hold your saw firmly to the panel as it will want to "ride up" on the blade stroke and lift off the material, loosing control.