What's the best way to get from Freiburg (Germany) to Hannover (Germany)?

As @iHaveacomputer already said, you could consider using a Mitfahrgelegenheit, a form of car-sharing.

At the moment, this is by far the cheapest way to travel in Germany.

People planning to drive to a certain place at a certain time announce that on the Internet; people looking for a ride to that place contact them, and ride along.

There are two major web players on the Mitfahrgelegenheiten market:

• mitfahrgelegenheit.de
• mitfahrzentrale.de

mitfahrgelegenheit.de does not charge community members for contact information; it is available immediately, and publicly. That makes it the superior choice IMO.

In contrast, mitfahrzentrale.de's business model is to charge the seeker looking to contact drivers. For payment, you either call a premium telephone number (charging €1.86 a minute at the time of writing; I do not know how many minutes it takes to get hold of the data.) or pay through bank payment. Both options may not be available to you as a traveler.

Using a Mitfahrgelegenheit is not always a 100% reliable business. Appointments are usually made by E-Mail or phone, and sometimes, people will simply not show up - although naturally, the drivers usually do. Mitfahrgelegenheit.de is offering a booking and payment system that allows for reliable reservations, but the vast majority of rides is still worked out by phone.

Still, this is a very cheap and potentially pleasant way to travel the country and get in touch with some locals - the ride you are looking for averages at between 25 and 35 Euros. The regular high-speed train fare (without advance reservation and special deals) is about 113 Euros. There are cheaper train options, but they usually entail excruciatingly long travel times on crappy trains with lots of changeovers.

Fast and safe would be the train, however this is not exactly cheap unless you have a "Bahn Card". For fast and cheap try http://www.mitfahrzentrale.de/ . I would say it's pretty safe, since people in Germany don't carry that many weapons anymore since 1945, however some people tend to be unreliable, or late... even in Germany :)

I think that are you only 2 options that make sense if you don't have a car; there is no long distance overland bus system like greyhound in Germany.

As others have mentioned, Die Deutsche Bahn, or Mitfahrgelegenheit is probably the cheapest option.

But for the sake of completness I want to mention Eurolines. It is a coach company that connects all big cities in whole Europe. I personally used it for example to travel from Tallinn to St. Petersburg. It is relatively cheap, reliable and comfortable. The coaches are generally in a good form.

There are also some connection that travel between different German cities.