Where to start on Ukraine? I thought I would list some of the better articles I have read on the issue recently. Basically comes down to this being Putin's last stand.
Here is an article encouraging the US to use energy as a weapon, namely to begin exporting crude oil and Liquefied natural gas. This would increase the energy security of US allies in Europe and make a dent in Russian profits. It will take another 3 years at best before we see any changes, and probably another 5 before a meaningful impact happens but once it happens Putin's power will decrease significantly.
Daniel Treisman is one of my favorite Russian experts, here is his piece on Putin. In an interesting comparison to Putin's 2004 Ukrain strategy, he basically states that this isn't the smartest move by Putin. It would have been better to let the new Ukrainian regime self implode. Before the crisis the EU was not willing to offer the loans or support that would have been needed to keep the Ukrainian economy going. While Putin's Ukraine policy will increase his domestic support in the short term it will hurt his standings in the long term.
Dmitri Trenin enables us to understand the Russian perspective on the crisis. While Trenin's predicting doesn't have the best track record, his ability to describe the Russian perspective to a Western audience is second to none.
For an analysis of the succession argument in Crimea take a look at this piece from the Washington post. This piece does a great job of putting things into perspective. When does a population have the right to succeed? How does this situation relate to the Kosovo situation?