The proposed schedule was Vista is to be released to manufacturing on August 9, 2006, and be broadly available by November 15, just in time for Thanksgiving. However, that's always subject to change. (I seem to remember an announcement that Vista was due out in early 2005, then late 2005, then early 2006...well, you get the picture.)
Some quick notes you may not know:
* There will be 7 (seven) different versions of Windows Vista: Starter Edition, Home Basic Edition, Home Premium Edition, Professional Edition, Small Business Edition, Enterprise Edition, and Ultimate Edition.
* Pricing is not yet known, but Starter Edition will be sold in mostly third-world countries at a reduced price, and Home Basic and Professional should be close to their Windows XP counterparts ($200 and $300, respectfully, with upgrades being about $100 less).
* It will be available in both 32-bit and 64-bit forms.
* All versions will be included on one disk. That makes it easy if you want to upgrade, since you'd just need to order a new key online, pop in your CD, and be upgraded in a matter of minutes.
* The requirements are not set in stone yet, but if you want to be able to take advantage of Vista's full potential, including AERO (the new graphics system), you'll want to have a minimum of a 2.2GHz Intel P4 processor (or AMD's equivelent), 512MB RAM, and a decent stand-alone graphics card (not integrated graphics). Of course you can still run Vista on older hardware (the basic requirements aren't much higher than that of Windows XP), but you'll be stick in a 'reduced graphics' mode.
Hope this helps,