According to the latest news, Russian forces are pulling back from the Ukrainian border. It looks like this particular crisis might be winding down. That being said, diplomatic negotiations are still ongoing and the troops might not be withdrawing all that many or all that much.
Here's an idea I had that might permanently deal with Ukraine (and Eastern Europe) as a flashpoint between Russia and the West. A grand bargain, if you will:
*Allow Russian annexation of Crimea, southern and eastern Ukraine, and Transnistria. Those areas are Russian-speaking and (generally) fonder of Russia than their Ukrainian kindred further west.
*Immediately allow western Ukraine (henceforth to be called Ukraine) into NATO and the European Union. The same with Moldova, with or without annexing Moldova into NATO/EU member Romania.
*Not sure what to do about Belarus. It seems to be a puppet of Russia anyway so if Putin leaves it be or decides to bring law into alignment with fact and annex it too, oh well. It's not a NATO country.
I imagine a lot of people will scream that this is appeasement, but Europe--whose primary problem this is--seems rather ambivalent about the Crimean situation rather than freaking out about the Russian armies being on the march. Furthermore, the US is poorly-placed to intervene.
As long as NATO exists and stands strong in defense of its member states, a cold-blooded calculating crocodile like Putin is not going to do anything too obvious. Though Russia is a powerful state, it is vastly weaker economically than the U.S., let alone the combined West. Russia is dependent on selling oil and gas to sustain its power, which is not a good thing in the long run even if it does give them leverage with the European countries that buy its gas.
Look at the Cold War. The USSR stomped on states in its own sphere, but despite its vast military power extending much further west than today, NATO kept Western Europe safe. The West is even stronger vis-a-vis Russia today than it was during the days of the Cold War. This formalizing of the spheres of influence of "the West" and Russia in Eastern Europe will give everybody something they want, let Putin save face, and eliminate the East-West tug-of-war over individual countries as a potential cause for instability and even war.
So let the Russians have some of their old sphere. Let them think they're standing strong against the homosexual drug-dealing fascists or whatever of the decadent West. My proposal, if implemented, leaves Russia "reigning in hell" so to speak, in the long run doomed to stagnation apart from Europe proper and contained by the NATO alliance without any non-NATO countries (in Europe at least) to easily bully.