That difference of opinion between Russia and Georgia that I mentioned earlier this morning? Well, it's gone hot. According to available reports, Georgia has shot down at least two to four Russian warplanes, Russia has been bombing Georgia all day, and a Russian armored column of 150+ vehicles is rolling into Georgia. Russia is claiming it has received reports of ethnic cleansing in villages in South Ossetia. South Ossetia is trying to break away from Georgian control; Georgia claims to have taken control of the South Ossetian capital of Tshkinvali, and is accusing Russia of arming Ossetian separatists.
Everyone involved seems to be trying to avoid saying so in so many words, but it looks like Russia and Georgia are now de facto at war.

T72 heavy tanks roll through Georgia (credit: Welt.de). Unclear whether these are Russian or Georgian. T72 variant, either way.

Georgian DANA 155mm self-propelled artillery on the move (credit: BBC)

Hind-D attack helicopters (credit: BBC)
See also: Photo gallery from Der Spiegel
(Pointer credits include luxobscura,
tommx,
james_nicoll)