A big question we get asked around here is from people wanting to know when is the right or wrong time to buy a new computer. It's not an easy question to answer, because there is always something new around the corner, so it's almost never the perfect time.
If you're in the market for Apple products, however, there is one website that tracks the history of Apple release timings and offers a handy buyer's guide that gives a good indication of when you should buy or when you should wait just a little bit longer.
Check out the MacRumors Buyer's Guide to get some very useful guidance.
Here you will see all the main product categories from Apple, and historic data on how many days have passed since the last product update and how long on average it takes Apple to update them. They have a nice traffic light system so you can see when something has recently been updated, when something is mid-cycle and when it's getting too close to a new update to be the right time to buy. Now you'll never be caught buying an iMac just a few weeks before something new hits the market.