The hot one this weekend, launched by AppleInsider and embellished by the sites that feed like pilot fish on its scraps (see here), is that the company has told its resellers that supplies of iMacs — Apple’s most popular desktop computer — will be “constrained in the immediate future.”

“A sign,” writes AppleInsider’s Katie Marsal, “which this late in the product’s life-cycle ‘only means one thing’ — namely that the company is drawing down inventory levels ahead of new models.” (link)

A nugget of news like that is all the Apple rumor mill needs to start its speculative engines, spinning out all sorts of putative specs, from an Intel quad-core CPU to a Snow Leopard operating system.

One reader in a MacRumors forum has already posted a tentative iMac price list (from $999 for a 3.00 Ghz dual-core model to $1,899 for a 2.83 quad-core machine). Another predicts that the new models will be unveiled Sunday, Feb. 1, in a high-profile Super Bowl ad harkening back to the one that launched the first Macintosh 25 years ago. (link)

But before you get out your credit card, you should know that reports of impending iMacs have been kicking around for more than five months. They started August 27, 2008, four months to the day after the last iMac refresh.

How do we know this? Because MacRumors tracks such things, including stats like days-since-update (278), in its helpful MacRumors: Buyer’s Guide.

Here, in chronological order, is the official Buyer’s Guide history of this season’s crop of iMac rumors:

• Aug 27, 2008: iPods, Notebooks, and… iMacs before the Holidays?
• Sep 24, 2008: New Mac Part Numbers Found in Future Shop’s Inventory? [Update]
• Oct 17, 2008: New iMacs Still Coming Before Holidays?
• Oct 28, 2008: Buyer’s Guide Update: iMacs, Mac Minis, and Mac Pros
• Oct 31, 2008: Whispers Suggest a Mid November iMac and Mac Mini Update
• Nov 03, 2008: Apple: No New Products Before Holidays
• Nov 19, 2008: Apple Waiting on Quad-Core Desktop CPUs for January?
• Dec 19, 2008: Evidence that Next iMacs and Mac Minis to use NVIDIA Chipsets
• Dec 23, 2008: New iMacs Shipping January 2009?
• 01/04: Macworld San Francisco 2009 Rumor Roundup
• 01/12: Macworld San Francisco 2009 Rumor Wrapup: Winners and Losers
• 01/20: Apple to Use Newly Released Quad-Core Desktop Processors?
• 01/26: Analyst Speculates on iMac Delays: Quad vs Dual Core?
• 01/30: Limited iMac Availability Suggests Possible Refresh

See also: Why the iMac is late