<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by TravelScholar:
You CANNOT purchase a German railpass once you get to Europe! So, if you're going to do the pass, then make sure you purchase it in the states before you go, and allow enough time for them to ship it to you.</font>
According to the Deutsche Bahn page on rail passes, some German Rail passes can indeed be bought in Germany (note the fifth paragraph under the heading "Making Tracks for Germany") :
http://www.bahn.de/pv/view/int_guest...ans_2003.shtml
Outside Europe the GermanRail Pass offer is available through travel agents with rail sales. You also can buy the German Rail pass (5 or 10 days passes, prices are calculated in Euro) at selected train stations in Germany (Aid Offices), for example at the airport in Frankfurt.
However, it seems that only the 5-day and 10-day variants are sold in Germany, so if a different length is needed, it would have to be obtained ahead of the trip.