Check out the great post by Ken Edgett on potential landing sites for the Curiosity (it will take me awhile to get comfortable with the now official name for the Mars Science Laboratory rover) at http://www.planetary.org/blog/article/00001967/
Editorial Note: These are all great sounding candidate landing sites. However, I'm uncomfortable with the process for selecting a landing site for once in a decade or two decade flagship rover. I would have preferred to send cheaper rovers to several sites to scout out the terrain and chemistry before committing a flagship class rover. I know that this puts me at odds with the planetary community. But what happens if the clays at the site selected turn out to be thin veneers created by dew? The MER rover landing capabilities were substantially enhanced to allow landing by Spirit at Gusev Crater, it it turned out not to be an ancient lake bed.
Your dissenting views welcomed!