Here's the sharpest optical image shown today of the Moon, from Palomar Observatory. You can see a notch in the bright mountain ridge in front of the crater, and a sunny spot on the far wall, which together appeared to look like a plume and its shadow in the much blurrier MMT image posted earlier. I see no plume in this image, and Jennifer Heldmann, who coordinated the Earth-based observations, didn't see one either.
EDIT 8:50 a.m.: I've replaced the image I originally posted (which came from a PDF file posted on the LCROSS wbesite) with one that came directly from Palomar Observatory, which is slightly sharper and presumably at its correct native resolution.
Palomar Observatory / Caltech
Palomar Observatory Adaptive Optics image of Cabeus after LCROSS impact
This sharp image of the crater Cabeus near the Moon's south pole was taken by the Palomar Observatory's 200-inch telescope using its adaptive optics system. The image was taken at a near-infrared wavelength of 2.1 microns. No impact plume is obvious, but analysis of the data may yet reveal something subtle in the shadows within the crater.