German-taxation.com - General information about German taxes and social security withholdings. Calculate your own income tax and social security contributions. - http://www.german-taxation.com/
Wolfgang Steubing AG - Broker in Frankfurt/Main provides information about business activities, like trading, selling, research and IPO-service, and company history. - http://www.steubing.de/index_e.html
Deutsche Boerse AG - Includes information, market data, DAX index, Xetra trading platform, listed companies, news, and the Frankfurt Stock Exchange. - http://www.deutsche-boerse.com/