Please sign a petition and help thousands of people from Australia, Canada, Mexico,the United States and many other countries protest the Belo Monte mega-dam project in the Amazon jungle. Work has already begun on the third largest dam in the world and is predicted to flood 400,000 hectares (nearly a million acres) of rainforest and displace over 40,000 natives, not to mention its impact on flora and fauna. Belo Monte's reservoirs will generate enormous quantities of methane, a greenhouse gas that is 25 times more potent than CO2.
Here is a great link to a site called Amazon Watch with plenty of information about this disaster in the making.
There are several available websites with petitions.
You can sign a petition here, or here.
Another effective form of protest is tourism. You can boycott the Brazilian Government by not travelling there.
Write a letter to Brazil’s department of tourism here.