Fascinating article in this week's New Yorker about the penny and all of the failed attempts to get rid of it:
A penny minted before 1982 is ninety-five per cent copper—which, at recent prices, is approximately two and a half cents’ worth. Luhrman, who had previously owned a company that refined gold and silver, devised a method of rapidly separating pre-1982 pennies from more recent ones, which are ninety-seven and a half per cent zinc, a less valuable commodity. His new company, Jackson Metals, bought truckloads of pennies from the Federal Reserve, turned the copper ones into ingots, and returned the zinc ones to circulation in cities where pennies were scarce. “Doing that prevented the U.S. Mint from having to make more pennies,” Luhrman told me recently. “Isn’t that neat?” The Mint didn’t think so ... [newyorker]
I can't remember the last time I've spent a penny as part of a cash transaction. I'm not quite as bad as Aaron (circa the Stack 'em High incident); I usually just leave them on the counter or accumulate them in a big glass jar.