In a display of dexterity that's quite admirable for her age, Spirit has photographed her underside with her miscroscopic imager instrument. It's not something that this particular camera was ever intended for, so the resulting image is out of focus, but you can still see the rover's wheels embedded deep in the soil.
As well as helping the rover team to understand the situation, this image may also help them discern whether any of the ground beneath the rover is potentially hard or sharp enough to do her an injury.
The angle of the picture accurately depicts the angle at which Spirit is currently resting. The distance between Spirit's wheel tracks is about one metre.