The ones that come to mind are the ones by RitaMae Brown, who actually puts her cat's name, Sneaky Pie Brown, right on the title page as co-author. Also, I don't know the author's name but there's a series about a cat called JoeGrey. And another where the only detail I can remember is the name Alice Nestleton, don't know if she's a cat or a person.
And of course there's the "The Cat Who..." series by LilianJackson Braun. I confess to reading some of these as a teenager. The main character is a guy named Jim Qwilleran, and he is always having to solve mysteries, and his two Siamese cats, Koko and Yum Yum, are always leaving clues around to point him in the right direction. Also, Qwilleran's mustache tingles whenever he's about to make a discovery.
Oh, did I mention that I think JoeGrey actually talks with his human in English?