Joshua Tucker, a political science professor from NYU and blogger at the Monkey Cage, has this opinion piece in the New Republic:

In short, little related to this war has changed; despite the Russian military victory, neither side can really claim to have gained much. So what are we to make of the conflict? Four explanations for why the war occurred seem plausible. First, it may have been a “mistake” on Georgia’s part. It’s possible Saakashvili guessed wrong, thinking he could grab South Ossetia and get back under the West’s protection before Russia did anything. Second, the war may have been a “mistake” on the part of a Russia determined to remove Saakashvili from power. Perhaps Moscow underestimated what the international community’s reaction would be and/or overestimated the capabilities of the Georgian opposition to Saakashvili. Third, as I have suggested previously on this website, the war may have been an attempt by the Russians to send a costly “signal” about its concern with growing Western influence in the former Soviet republics–in particular, vis a vis Georgian or Ukrainian NATO membership. Finally, the war may have been the start of a series of aggressive moves by Russia to reclaim parts of its former empire by force, as John McCain seemed to suggest last fall.