A while ago i needed a way to look up addresses from zip codes in Brazil for a weekend tinker project (Zip codes are called "CEP" here, "Código de Endereçamento Postal", or Postal Addressing Code). Turns out such a database is pretty hard to get hold of. Zip code data is created and maintained by the Brazilian Post (Correios), they have a copyright on it and are selling it for a hefty price tag. There are two versions for sale, "DNE Básico" for R$1.100 (complete dataset in text format, probably CSV), and "DNE Máster" for R$2.500. As far as i aware, the "Máster" version is just the same as the "Básico" version, but additionally contains the database in MS Access format. Okay, both are a bit above my budget.
Luckily there is another option, called "Guia Postal Brasileiro Eletrônico", or GPBe. This is an executable that you can run on your PC to manually query zip codes and addresses. And to be able to do that it must somehow contain the entire database in some form. It costs R$50, which is affordable (about US