Killzone: Liberation UMD seems to be sent to random PlayStation Underground members and will also be available on newsstands in the next Official US PlayStation Magazine. But there are two more UMD demos to be clamoring for now: Gangs of London, which we assumed would no longer arrive after the game's website stopped taking orders for demos. SOCOM: Fireteam Bravo 2's demo UMD can be secured by pre-ordering the game at GameStop. That seems a little dumb (aren't demos supposed to help uninterested people in purchasing the game?) but maybe you can hassle your local GameStop employee to give you a disc for free, sans pre-order.
[Via IGN Boards]