Best Pre-Paid Data Plan For a Visit To Germany?

code prole writes "With two upcoming trips to Germany, and no readily available Internet (Wi-Fi or otherwise) in the location where we'll be staying, I'm looking for a no-contract USB stick and pre-paid data plan. Vodafone has a huge selection of USB sticks but has proven to be unresponsive to questions about data plans. And the US-based T-Mobile Help Center was clueless about getting the device in Europe and using it there. Hopefully the Slashdot community has some suggestions. Any duds to avoid?"