We have a good friend who just bought an apartment in Sao Paulo a couple months ago and had to buy everything from furniture to appliances to electronics for her new place.
She got a good tip from a friend and bought almost her entire new house at this one store, it is called " "ARMAZEM 7" which means "WAREHOUSE 7".
ARMAZEM 7 is an discount warehouse that sells new stuff clients just returned to several different stores for no reason other than changing their minds about the purchase.
Traditional stores don't like to deal with trying to sell returned TVs or Refrigerators out of the original factory packaging so they sell it to ARMAZEM 7 which sells it at a good discount.
My friend saved R$500,00 on a brand new stove and over R$700,00 on a large screen LCD TV.
I haven't tried it personally but heard great things about it.
If someone knows them and want to share any impressions or feedback please let us know.
Another tip is "E-BIT" which is a website where you can compare prices of different products online, from Airline Tickets to Books, you can rate your consumer experience at a given store and also see what review other people have given such store or company, everything from TAM Airlines to your local grocery store or pharmacy. The site rates them according to price, customer service etc...