As of 3:30 p.m. EDT today, the $29 Snow Leopard and the $49 Snow Leopard Family Pack were ranked No. 1 and No. 2, respectively, on Amazon's software sales chart. The $49 Family Pack provides licenses for five Macs.

Although Amazon has been taking pre-orders since early August, Apple's own e-store, as well as other online resellers, only kicked off theirs sales today. Apple does not rank its software sales on its site, although it does for its Mac, iPod and iPhone lines.

Snow Leopard, or Mac OS X 10.6, had on Amazon's bestseller list within days of the giant online retailer posting the product for pre-order. Since then, however, both had slipped, with the $29 single license often holding down the No. 3 position.

Windows 7, which is slated for an Oct. 22 release, had grabbed the lead spot on Amazon's software bestseller list when two editions were heavily discounted during a two-week sale earlier this summer. Microsoft's new OS was absent from the chart today, however. Today, Windows 7's best showing was the $119.99 Home Premium Upgrade, at No. 31.

Microsoft's highest-placed product was Office Home and Student 2007, at No. 3. Amazon is selling the $149.95 application suite for just $69.99.