For a limited time, you can get PB:W's entire back catalogue as free downloads from their website. Some of the old EPs can be difficult to find today, and it's hard to say no to free (good) music. :)
For an allround impression of their music, I recommend Demokratischer Sektor, while the albums are mainly ambient stuff.
http://patenbrigade.com/download
Of course, you need to give your e-mail address, so they can keep track of the downloads - they'll reply back (manually apparently, it took some hours for me) with links to the downloads.