It turns out those leftover slices still sitting in the box on your coffee table from that pizza you got delivered, should have been thrown out a long time ago, but those steaks in the freezer are good for 6-12 months.
At Makezine.com’s Tools-N-Tips, there was a link to AlgerWiki, containing a good reference to expiration dates for food items.
(The link no longer works September 23, 2009; here is Google’s cache of the page)