Here are tons more additions to The Best Sites To Learn About Mardi Gras & Carnivals:

Rio Carnival 2012: costumes and celebrations is a slideshow from The Guardian.

In pictures: Rio de Janeiro carnival is from The BBC.

Rio de Janeiro Carnival 2012: the first night of parades in the Sambadrome is a slideshow from The Telegraph.

Here are several CNN videos:

Brazil’s Big Party:

Carnival Has Started in Brazil:

Carnival in Seychelles:

Celebrating Carnival in Trinidad:

The good times roll at Mardi Gras: