About 3ft – in the hall the other side of the wall the sofa sits against – mini-aracer's new Cnoc 14. Second closest is ~8ft away – that's vertically, as it's sitting in the spare bedroom almost straight above my head!
Would have been winning this one a year ago before I got the laptop, given the trainer has a bike sitting on it right in front of the old computer. But that's 15-20ft away, which is probably about equidistant with the rest of the stable in the garage (another 9 to 11, depending on how you count component kits which could be built into bikes and partially built bikes).