Apple's real close to introducing new computer models, which means that all the retailers are gearing up to clear the shelves of the old one. There are bargains to be had. This one, from Other World Computer, just hit my inbox, but there are bound to be others as well. (No endorsement of OWC expressed or implied.)
These are brand-new machines, and they come with the full warranty. They are not the latest, greatest, super-duper, bleeding-edge machines they once were, but they're perfectly fine for 99.8% of what normal users have occasion to use them for. If your current iMac is 5 years old or more, hey, a 1-year-old model is still a step up, right? And the price will be right for the next month or so.