Other than UV filters, what are good general purpose filters to have. I have a Hoya CPL filter on the way now, but I was trying to figure out what else I should look at picking up in the near future. I'm trying to cover as many of my basis before hand as I get more and more practice with the camera, for all types of photography. I was thinking probably a ND filter as well, but I wasn't sure if any other filters were good general purpose filters to have, or if everything else such as skylight and specific color filters were for more specific projects and looks. Thanks for any input.