What should we do?
I really think we should do something, and quickly. I was in the US during 9-11, and I saw how rapidly the media twisted people's genuine feelings of shock, disbelief and horror into almost rabid hatred and racism, and so feel it's really important to move quickly. People's reactions to this tragedy could go either way - like in Spain blaming the government for making us a target, or into anti-Arab/Muslim sentiment and support for more aggressive foreign policy and more repressive domestic legislation. I don't know what's going to happen...
I've emailed the StWC to see if they're planning some kind of demonstration... but the only really concrete thing I can think of right now that's achievable could be a flyposter campaign in London, but that'd only be useful if people were willing to help put them up...
What stuff can people think of - is it worth trying anything?
What would it say on the posters?
Edited to add: genuine question. Not having a go.