Currently when I want to wipe a USB disk with pseudorandom data in Linux I do the following:
dd if=/dev/urandom of=/dev/sdb conv=notrunc
urandom is very, very slow, it gets to the point where the bottleneck is not the device.
I know of another method -- the Mersenne twister. This is used in one instance by DBAN as a PRNG to securely erase data with, and it is easily 'random' enough for wiping drives -- and it is very fast. However, I'm not sure how I would use it in Linux. Is there a Mersenne twister program which I can then pipe into dd to wipe drives with?