The official Brazilian Post Office site. (In Portuguese).
Established in 1968, the Brazil Philatelic Association (BPA) explores all aspects of Brazilian philately. It has published more than 160 issues of its quarterly journal, Bull's Eyes, since becoming an active affiliate of the American Philatelic Society in 1970.
See all Brazil stamps in the StampWorld free online catalogue.
Recent news about Brazil stamps, from StampNews.com.
Wikipedia listing of people depicted on the stamps of Brazil, with links to biographical data.