Hello Corrado,

the DNIT maps are updated and give a good overview,
and the Tracksource for Garmin are superb!
Other street maps (produced in the states) you will find here:
http://www2.transportes.gov.br/bit/mapas/imapa.html

A Google like online map is Maplink, it's more precise:
http://maplink.com.br/

But I am a fan of topographic maps and I like to take quiet road and tracks, so I discovered the IBGE maps. 2008, when I did the first trip to Brazil, I bought some of them in Rio, but it's rather hard to get the paper maps, many are out of print.
Most of the maps can be downloaded nowadays. There are also topo maps from DSG (military) and SUDENE (development agency). They cooperate with IBGE.
Try here to download maps:
http://biblioteca.ibge.gov.br/ or at ftp://geoftp.ibge.gov.br/mapas/

Or use the viewer at:
http://mapas.mma.gov.br/
With WMS-compatible software you can download maps there.

Here are some map examples:
Jaguaribe 1: 1 000 0000
Refife NO 1: 500 000
Estância 1: 250 000
Salvador 1: 100 000
Ouro Preto 1: 50 000
Colônia Pereira 1:25 000

But there's one disadvantage: Most of the maps are rather old (1970's/80's). But topography doesn't change normally...

Maybe you would like to buy Guia Praias from Quatro Rodas, a popular brazilian map publisher:
http://viajeaqui.abril.com.br/guia4rodas/lancamentos/guia-praias.shtml

Ciao
Helmut

P.S. I use CompeGPSLand to plan my trips and the TwoNav Sportiva GPS receiver outdoor:
http://www.compegps.com