The Samsung Galaxy Tab Tube test programme will offer up the device for a 48-hour loan on Monday, Wednesday and Friday of each week up until the product's official launch on November 1st. To get in on the action, you need to email firstname.lastname@example.org or just turn up at one of the stations (Ealing Broadway, Liverpool Street, Highbury & Islington or Balham) and talk to a Samsung promotionbot. Full details on T3's site.
Let us know if you test drive, sorry, "test Tube" it. I'll also have a look out for them, although I imagine it will be a while before I see them more frequently on the Tube, like the iPad. Hat tip to Michal for letting me know about the trial.