Vodafone Germany has prepaid data called Websessions. The APN is event.vodafone.de. This is extremely good and pretty cost effective. Travelers to Germany can get a Vodafone sim card (Call Ya Prepaid) and enter the above APN settings in their phone or tablet.
Data costs Euro 3.95 per day for 1GB or 12.95 per week for 1GB. Speeds are pretty decent in major cities.