In addition to its 20€ a month prepaid unlimited data offer, Blau is now offering a USB data stick for 99€ + 5.90% shipping which includes a Blau SIM card and 20€ credit. A bit expensive compared with the other USB data stick offers, but worth mentioning. The stick is SIM unlocked and supports HSDPA, even though UMTS is the highest speed you'll get on Blau (E-Plus). No mention of whether it supports 3G bands other than 2100.
blau.de Surfstick with Flatrate Data