Strategy Page reports:
June 18, 2009: The U.S. Army has ordered 38.4 million rounds of .300 Winchester magnum ammunition for its newly modified M-24 sniper rifles, as well as similar SOCOMs Mk13 models. The new ammo will cost about $1.30 per round. The .300 Winchester magnum will be ordered in minimum lots of 56,160 rounds (117 boxes of 480 rounds each). The entire 38.4 million rounds will last a while.
$1.30 a round! I would have thought they could get it cheaper than that!
There is a discussion at SaysUncle about the pro’s and con’s of the cartridge.
Thanks to David for the link.
UPDATE:
A more factually correct article is at Defense Industry Daily, and it quotes regular TFB commenter Daniel Watters.
D.E. Watters of The Gun Zone adds that .300 Win Mag is used in the Mk13 sniper rifle, another Remington 700 long receiver derivative that’s assembled from parts at NSWC Crane. The most recent version is the Mk13 MOD 5, which allows the use of the same sound suppressor as the Knight’s Armament Company SR-25/MK11 sniper rifle.
Blaser, in partner ship with Norma, will be introducing a new line of magnum cartridges later this year. They are not giving out any detailed information until May, but they have said these are completely new cartridges, not based on any previous designs.

7mm Blaser Magnum, .300 Blaser Magnum, .338 Blaser Magnum and .375 Blaser Magnum
Factory cartridges will be sold by Blaser and Norma and will be available in August along with Blaser R93 rifles chambered for them.
More info here.
New for 2009 is the Kimber Model 8400 Police Tactical chambered in .300 Win. Mag. The rifle is designed with military and law enforcement in mind.

The previous Kimber tactical rifles based on the 8400 action got good reviews and I expect this one will not be any different.
I will update this post as more information becomes available.
Browning will be releasing a line of A-Bolt Target rifles.

The rifle will come in three calibers: .223 Rem., .308 Win. and .300 Win. Mag. It is a pity they are not offering more exotic calibers. The stainless model will cost $1489 for .223 and .308 while the .300 will cost $1519.
More info @ Accurate Shooter
The photo below shows a couple of South Ossetia militia. The guy on the right is carrying a Sako TRG.
It is unlikely Finland would allow arms exports to South Ossetia. It was probably bought on the civilian market and then exported. I cannot imagine that South Ossetia would have many snipers so this is feasible.
Their squad sharpshooters (or whatever they call them in that part of the world) are probably using the SVD.
I cannot make out if it is a TRG-21 / 22 (.308 Win) or TRG-41 / 42 (.338 Lapua or .300 Win Magnum). I have never seen a photo of a 41/42 without a muzzle break, but I think the 21/22 can have the Sako TRG muzzle break attached, please correct me if I am wrong.

Click to expand the image
H/T: MP.net