For those interested, the reason the "anti-imperialist" left isn't doing anything is because virtually nobody agrees with each other about the situation.
The ANSWER coalition and the IAC, who organized those massive anti-war demonstrations in DC, are arguing that the protests in Ukraine were staged by the US/EU and Russia's actions are defensive in nature. If they organize any demonstrations, they will take the line of "EU/US Hands of Ukraine" or some such, not "Russia out of Ukraine." If they try to organize such a demonstration (and I expect that they will), virtually nobody will show, because nobody else agrees with that nonsense. "No war in Iraq" was something a screaming ****ton of people agreed with, hence the giant demonstrations.