You can find a lot of information about Open Access on the information platform open-access.net which is supported by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG), the German Rectors' Conference, and many scientific organisations.
The Directory of Open Access Journals offers a comprehensive list of open access magazines.
The Sherpa/Romeo list will give you details about which publishers allow secondary publications on the University website for which magazines.
Large scientific and research organisations, the German Rectors' Conference, and the Otto Friedrich University support the open access philosophy as stated in the Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities.
The alliance of German scientific organisations has published Frequently Asked Questions about open access and secondary publications rights where you can also find numerous interesting details and facts.
The German UNESCO Commission has published an Open Access handbook which talks about possibilities and challenges of this model and looks at the topic from different angles. The handbook is available for download on the website.