Obviously the best answer is right after Apple has made an update. From what I have noticed this typically happens in February, July, or Sept/October. Apple is scheduled to release Snow Leopard September this year.  I would suspect there may be a new Apple product (tablet) lurking around the corner.  Check out the rumors here: http://www.9to5mac.com/Tablet-Apple-September.  Here is a site that has kept track of what has happened historically and tries to make what I would consider the best recommendation of when to buy: http://buyersguide.macrumors.com/.  Looking to buy an Apple computer or an iPod?  Check out my store here: http://ryan.lusvardi.net/store