Apple is getting everything in place for the release of OSX 10.8 “Mountain Lion” due later this month.
The names of the Macs that will be able to run OSX 10.8 “Mountain Lion” have been published on the Apple website :
http://www.apple.com/osx/how-to-upgrade/
From eldest to newest these Macs are :
– iMac “mid 2007” or newer (so any “Aluminum” iMac)
– MacBook Pro “mid/late 2007” or newer (so any MacBook Pro with an NVIDIA graphics card)
– Mac Pro “early 2008” or newer (so any Mac Pro with the Xeon 5400 “Harpertown” processors or newer)
– MacBook Air “late 2008” or newer (so any MacBook Air with Thunderbolt or MiniDisplayPort)
– MacBook “Aluminum” = “late 2008″ (so the 13” MacBook Pro look-alike)
– MacBook “White – early 2009” or newer (so only the ‘original’ white polycarbonate design versions that have an NVIDIA graphics card)
– Xserve “early 2009” (so only the latest generation with Xeon 5500 “Gainestown” processors)
– Mac mini “early 2009 & late 2009” (so only the original Mac mini design that have an NVIDIA graphics card)
– Mac mini “Aluminum” = “mid 2010” or newer (so any Mac mini of the extra flat redesign)
…that’s the bad news (for some – those of us with older Macs…)
and the good news is :
you don’t need to have MacOSX 10.7 “Lion” installed to upgrade, you only need MacOSX 10.6 “Snow Leopard” with the “Mac App Store” application (since OSX 10.8 “Mountain Lion” is only available from the Mac App Store…)
MacManus.nl 
note that it is completely unclear why not all Macs that can run MacOSX 10.7 “Lion” are able to upgrade to OSX 10.8 “Mountain Lion”…
as technical requirements Apple only lists :
– MacOSX 10.6.8 “Snow Leopard” or newer installed
– 2GB of RAM or more
– 8GB of free (hard disk) space
…that sounds like either :
– any Mac that can run MacOSX 10.7 “Lion”, should be able to run OSX 10.8 “Mountain Lion”, but the official installer will prevent you to to install on unsupported Mac (so a tweaked installer might enable you to install anyway…)
…or :
– Apple doesn’t want to list the actual technical requirements of supported hardware components (like minimal processor type, processor speed, type of RAM, type of graphics card, type of AirPort-card, type of display-connection, etc.)
based on what I’ve seen so far, my best guess is that the minimum requirements are :
– Intel Core 2 Duo “Penryn” or newer processor (so the Core 2 Duo “Merom” is no longer supported)
– “Mac App Store” application installed (so at least MacOSX 10.6.8 “Snow Leopard” installed)
– 2GB of RAM
– 8GB of internal free disk space (either on SATA-harddrive or SSD solid state)
– dedicated graphics card (so the shared memory Intel Graphics Media Accelerators like the GMA 950 and GMA X3100 are not supported)
– WiFi-N compatible AirPort Extreme wireless networking card
– display connection on MiniDisplayPort or Thunderbolt
another interesting thing to note :
in OSX 10.8 “Mountain Lion” the applications that we know as “Address Book” and “iCal” have been renamed into “Contacts” and “Calendar” (just like in iOS and on iCloud…)
OSX 10.8 “Mountain Lion” has been released this Wednesday (July 25th)
You can buy and download it from the Mac App Store
Thomas seems to have found a way to install OSX 10.8 “Mountain Lion” on unsupported Macs
Judging form his info, I expect his solution to work for any Mac that is now running MacOSX 10.7 “Lion”
look here for more info :
https://macmanusnl.wordpress.com/2012/02/11/10-7-3-refuses-to-see-the-atheros-ar9280/#comment-447
If you need to install OSX 10.8 “Mountain Lion” on multiple Macs, you might be better off doing so by creating a USB-stick with the installer on it (to bypass the need to do the rather download from the Mac App Store more than once)
for more info look here :
https://macmanusnl.wordpress.com/2012/07/27/tip-put-a-osx-10-8-mountain-lion-installer-on-a-usb-stick/