All the talk about NATO ships entering the Black Sea. Yes, that could be linked to the situation in the Ukraine but no, this is not a direct threat for Russia. These ships can "show the flag" - a very important Navy mission. They can also collect intelligence on the Russians. And they can show support for the insurgency. But in terms of military threat, the Black Sea is a lake by US Navy standards, which is waaaaaaay too close to the Russian Federation and its airpower and therefore not a place the USN would pick to attack Russia. People often assume that the main threat to a navy is another navy. This is not so, the worst threat for a navy is the other guy's airpower and any US ship in the Black Sea would have a zero chance of survival against the Russian air force, especially without a good air cover of its own. At this point in time, the US and NATO are not ready to commit enough airpower to engage in combat air patrols, nevermind a full scale war, over the Black Sea. In fact, the US has much better options to attack Russian forces in Crimea than sending ships into the Black Sea. Bottom line: these USN ship are not a military threat to anybody.
The US/NATO missile shield. Some have speculated that the US/NATO anti-missile shield being currently developed and deployed in eastern Europe could offer a protective umbrella under which NATO could attack or threaten to attack. Yes, this was the plan but no, this will not work. At this point in time the system is not really operational. Furthermore, Russia has the means to destroy it very rapidly (using Iskander missiles and Spetsnaz forces). Finally, this system is designed to intercept older generation missiles and not the advanced types currently being fielded in Russia.
I see no signs of the US or NATO gearing up for war against Russia. And, indeed, why should they when for a tiny fraction of the price and at zero risk they can simply buy off the security forces in the regions which oppose the insurgency? And in the unlikely scenario that Russia would use military force outside Crimea, nobody at SHAPE is going to go to war over Lugansk, Donetsk or Kharkov. Yes, they are every bit as evil as Hitler was but, no, they don't have his courage.