There is single point to cross border between Georgia and Russia: Verchniy Lars. It is open for the cars since March 1, 2010. Note that you have to get the Georgian and Russian visas to cross the border.
You can't cross the Georgian border from South Ossetia or Abkhazia territories! It is criminal in the Georgia, and you can get problems there.
According to this information, all you need to cross the border, is:
- If your country has an agreement with Georgia about no-visa crossing (such as Ukraine, Armenia, and so on), you simply must follow the rules of border-crossing of Russia and Georgia (see it on the official sites)
- If your need visa to visit the Georgia, and you have it, and you follow the rules of crossing the borders - you will have no problems.
- you can't get visa right at border in Verchniy Lars. You can get it at all the others official borders of Georgia, but not there. I think, this can be cause of problems for some peoples.
Also, there is a stats from various sites that there were some non-Russians and non-Georgians who cross the border.