Agency rating lists are sites or groups specifically devoted to collecting information about translation agencies from translators. These ratings are then made available to other translators, either for free or for a small fee. The idea is you check these lists before taking on a new agency client to avoid being caught out by bad or late payers.
Riccardo gives an excellent summary of the pros and cons of each of the following services: Payment Practices, Translator Client Review List, ProZ’s Blue Board, Translators Café’s Hall of Fame and Shame, the WorldPaymentPracticesFree group, the Translation Agency Payment group and TranslationDirectory.com’s Black List. Well worth a look!