Georgia Leaves CIS
Georgia has left the Commonwealth of Independent States (CIS), organization-successor of USSR, after the Georgian parliament's decision on 14th August 2008. The Russian-Georgian war in August 2008 became the key reason to leave the organization although Georgia had declared the intention to put end to CIS membership before.
Thus Georgia is a forth post-Soviet state which is out of CIS. The Baltic post-Soviet states Estonia, Latvia and Lithuania have never entered CIS. So now CIS consists of 11 countries including participating member Ukraine and associate member Turkmenistan.
Interestingly almost the same circumstances pushed Georgia to enter CIS in 1993 after rebels and Russian army had taken away the Georgian region Abkhazia and had made ethnic cleansing against the Georgians. Then the president of Georgia Eduard Shevardnadze hoped to get Kremlin neutrality or even support so that Georgia could restore the unity and return the lost territories. Initially Georgia had refused to enter CIS in 1991 as the Baltic States had done.
According the CIS rules, the terms of Georgia formal membership in CIS have finished on 18 August 2009, a year after the Georgian parliament stated Georgia left CIS (source, in Russian).