Just wanted to let you folks know, that since today Vodafone Germany are selling an unlocked 3G/USB-modem supporting HSDPA with up to 3.6 MBit/s and both European 3G frequencies (UMTS 900/2100) for just € 10 including a prepaid Vodafone SIM (and probably vouchers for a couple of hours of free internet access).
This promotional offer is prepaid (so without any commitment) and available
online (with free shipping) and in local Vodafone stores.
For replacing the Vodafone software with the original unbranded software from the manufacturer (ZTE) called "ZTE Join Air", check out
the 3G modem wiki.