As a result, I've spent a fair amount of time looking at the images. Basically, there are 2 types of anomalies discussed on this page

• What is That? - a number of rocks looks like fossils
• Anomalies acknowledged by JPL

Spirit Panoramic Camera - Sol 013	Several very thin objects, some with holes
Sprit Panoramic Camera - Sol 016	Several more thin objects that look like oyster shells and 2 or 3 that look like welks (small spiral conchs)
Opportunity Microscopic Imager - Sol 029	The only natural phenomena I know that causes angular shapes like these involve fossils in limestone. I can't wait to see what the analysis is.

"bunny rabbit" / "plant"

This is an obvious 3D object that cast a shadow. In the closeup stereo view, this object is obviously lying on the surface. The official explanation is that this was probably a piece of an airbag - ie, it is something we brought, not something that is a part of Mars. At any rate, the object is no longer visible in recent photos. Image (Stereo pair) Article

Fibers

The Opportunity Microscopic Imager has photographed fibers. One of these is obviously real because it is in focus in some images and out of focus in others. Some possibilities are, mineral fibers (bisolite, millerite, and the like), hair (contamination from the lander), synthetic fiber from the lander. The way it is just sitting on the surface indicates that it probably fell off the rover. The "other fibers" that go beneath the soil are not quite so obvious and might be just image artifacts. Main Image Related Images Article