It'd be really handy to have a bob-deinterlace filter for MPlayer along the lines of the one MythTV has, since it seems to produce good results on most displays. The approach is simply to double the framerate, doubling up odd lines on one frame and even lines on the other, making both fields visible at the cost of a bit of flicker on small details. (Presumably you can play with interpolating the alternate lines rather than just doubling them...)