Apple (AAPL) today confirmed what the analysts and rumor sites had already divined: OS X Leopard, the sixth major release of the company’s flagship operating system, will go on sale Oct. 26. Apple’s retail stores will start selling it at 6 p.m., local time. Its online store is already accepting pre-orders at $129 apiece.

Much of what the new OS does is already known, thanks to the lengthy previews Steve Jobs has given over the past year and a half and to leaks from developers working with pre-release builds. (See, for example, Prince McLean’s Road to Leopard series at AppleInsider.) But the order in which the company’s press release ticks off the new features telegraphs which features it thinks will be Leopard’s key sellings points:

• Redesigned 3D Dock with Stacks, a new way to organize files with one-click access
• Updated Finder with CoverFlow, so you can flip through files as you do album covers in iTunes
• Spotlight search of content from any computer on a local network
• Back to My Mac, which lets you grab files from remote Macs over the Internet
• QuickLook, which displays the contents of files without having to open the app that created them
• Spaces, a new way to organize files by project and to flip from one project to another
• Time Machine, the much-touted back-up system*
• A new version of Mail wih 3-D stationary designs
• Notes and To Dos that can be synced across multiple Macs and stored in Smart Mailboxes
• Data detectors that recognize e-mail addresses and RSS feeds
• iChat Theater, which adds slides and movies and Photo Booth effects to iChat video
• Improved parental controls
• The complete Boot Camp release (it’s not disappearing as some had feared)
• Web Clip for bringing widgets to the Dashboard
• New PhotoBooth features, such as adding backdrops
• An enhanced Dictionary with Wikipedia built in
• A new iCal that supports the CalDAV standard
• An updated Frontrow for watching movies and TV shows at a distance with Apple Remote

The biggest surprise in this list may be the relatively short shrift Apple gave Time Machine, the feature that generated the most buzz at Macworld. The reason for this may be hidden in the footnote at the bottom of the press release:

*Requires an additional hard drive sold separately.

Backups are the bane of every power user’s existence. Time Machine is a worthy attempt to solve this perennial problem, but because it requires advance planning and a big exernal hard drive, most users probably still won’t bother.

With only two weeks to go before the release of OS X Leopard, the fifth major revision of Apple’s (AAPL) flagship Macintosh operating system, AppleInsider today published the sixth entry in its comprehensive Road to Leopard series — and at Apple’s insistence pulled two earlier posts offline.

Written by Prince McLean, the nom de plume of a systems programmer who clearly knows his stuff, the series not only describes with text and screen shots the key innovations coming in Leopard, but it takes pains to place them in the history of graphical user interfaces as they evolved from Xerox Parc, through Lisa and the first Macs, Systems 8 and 9, Next and the previous versions of OS X. The Commodore Amiga even makes a cameo appearance.

The series is so good that Apple’s legal staff has stepped in, demanding through cease-and-desist orders that parts of the first two entries be removed. AppleInsider has taken them temporarily offline while they are being redacted.

[UPDATE: The first two posts are back up in heavily redacted form.]

If you’re interested in what’s in store for you when Leopard finally arrives, you might want to archive the other posts before key sections disappear. Here are the links:

• Road to Mac OS X Leopard: Preview 4.0 [redacted version]
• Road to Mac OS X Leopard: Dictionary 2.0 [redacted]
• Road to Mac OS X Leopard: Dock 1.6
• Road to Mac OS X Leopard: Finder 10.5
• Road to Mac OS X Leopard: Spaces
• Road to Mac OS X Leopard: Time Machine

With three weeks left before the promised ship date of OS X Leopard, the long-awaited and much-delayed sixth major update of Apple’s (AAPL) flagship Macintosh operating system, Piper Jaffray’s Gene Munster is already calculating its impact on the company’s revenue stream.

In a note to clients issued this morning, Munster observes that OS X Tiger, Leopard’s predecessor, was also released at the end of the first month of a fiscal quarter (April 29, 2005 vs. Oct. 26, 2007). He writes:

At that time, the OS X installed base was 12 million and Tiger sales added $125 million to the quarter. The Mac OS X installed base is now approximately 23 million, so we expect Leopard to add approximately $240 million to the Dec. 2007 quarter. This assumes similar uptake rates to the Tiger launch, which saw 15% of the user base upgrade in just 6 weeks (eventually 66% of the user base upgraded to Tiger).

Looking ahead to the next Macworld, Steve Jobs’ favorite venue for announcing new products, Munster anticipates one of two possiblities:

• a multi-touch PDA slightly larger than an iPhone (which some are calling the new Newton)
• an ultra-portable Mac that’s smaller than the smallest MacBook (which AppleInsider has dubbed the ThinBook)

“If Apple launches a new product at MacWorld in January,” Munster writes, “we believe it will likely fall into one of these two categories.”