Most perf testing tools have decent reporting functionality which output fairly self explanatory reports. For a more thorough approach however, have a look at this document: http://www.perftestplus.com/resource...s_Template.pdf written (i think) by Scott Barber. Hope that helps!
I always place the Executive Summary in the 2nd or 3rd item in the document, and write it with big bright graphs for attention challenged managers, with the rest of the document detailing the gory details. In addition, when I send a mail that the report is ready, I include the Executive Summary in the mail (graphs and all).