Apple released new iMacs and price dropped eMacs on Tuesday, Feb 4th, 2003. After each product release, MacRumors provides a wrapup of rumors to reveal the sources of the most accurate information.
Despite rumors of 19" iMacs last year -- Apple doesn't seem to agree. Beyond that, Spymac, MacOSRumors, and MacBidouille posted rumors in 2002 that the iMac would arrive at MacWorld San Francisco 2003. ThinkSecret put a stop to those rumors in the days before MWSF, and this information turned out to be accurate -- MWSF came and went without iMac upgrades.
Attention was drawn towards the PowerMac/Display upgrades in the subsequent weeks, with Thinksecret first suggesting Feb 3rd as a tentative week for iMac updates. Meanwhile MacRumors sources provided a solid date of Feb 4th, as well as definitive details of the high-end iMac upgrade (though midrange price point info was incorrect). Thinksecret then posted last minute price point of $1299 for the iMac, filling out the bottom end of the line, as well as details of eMac price drops.
MacNews.net.tc initially posted $999-$1699 specs which were echoed by Appleinsider immediately before the release. These specs were wrong, with no apparent basis, casting further doubts on these sources for future specs.
Summary
As mentioned before, accurate rumors are available... but with the influx of rumor sites, it's often difficult to discern accurate information from pure speculation.
It seems speculation and "predictions" are often passed off as rumors -- these practices should be discouraged and any purely speculative information is frowned upon (unless specifically stated as such), as it simply muddies the water and further incites unreasonable expectations amongst readers.
Some of this may be unavoidable, as frequently, sources of rumors may simply be based on unconfirmed reader contribution which has been known to miss their mark. 
