What you can do
In the United States: Get on the phones. Call your US Congressmen/women and demand they issue statements in support of the Iranian people. Remind them of Iran Freedom Support Act of 2005. Make sure to be polite and courteous. Call your senators and demand they be tough with the regime.
In Canada, UK, Holland & other European countries: Call your respective Members of Parliament. Demand they press their respective governments not to negotiate with the Iranian regime. Be polite and ask them kindly to issue statements in support of the people of Iran's quest for democracy and liberty. You can call or write to your media and ask them to cover the Iranian regime's brutal crackdown of the peaceful protests in any way they can. This is a media war. This is the information war. All of you regardless of your location can spread the word. The regime fears nothing like information. That's all I can think of now but if you've comments or suggestions, please share them with me.
You can find local pro-freedom rallies arranged by Iranian expats in your town/city and show up as a sign of support. Trust me, it is very heart warming for Iranians to see you care. All of us need to be encouraged and I am sure your presence provides that for those who are fighting the regime. Thank you!