Where can I find information on specific companies and their labour practices?
Search the Clean Clothes Campaign website to find general information, research and past and present cases of labour rights violations involving specific companies.
The following websites also offer substantive information about corporate behaviour toward workers, the environment, ethical and legal standards, etc.
Note that different websites may rank different brands lower or higher, because they can all make different choices in what specific aspects they consider more important, how well they trust company's own CSR reporting, etcetera.
Sourcewatch also has a guide on how to make your own assessments on a company's track record.