Everything's relatively quiet at the moment, but the following English-language Twitter feeds have provided useful comments and links about the Ukraine crisis:
Ben Judah (British journalist, causing a stir with his attacks on "Londongrad")
Maxim Eristavi (local freelancer, travels around Ukraine)
Miriam Elder (Foreign Editor at Buzzfeed, Russian specialist)
Oliver Bullough (another British [?] journalist and Putin-sceptic)
Lawrence Freedman (Professor of War Studies, posts on Putin's strategy)
Darth Putin (fake Putin twitter feed, black comedy)
I'll add more later...