Places in no specific Order
Kuttikanam (nice climate few beautiful plaes to go to) , Kumarakom (Bird Sanctuary , House Boat, er ...er.. Toddy

and beautifiul food )
Prakash has mentioned a few places also.
Yercadu, Ooty, Munnar (Well now it might be hard to find a place to stay here), Kodaikannal.
Theres quite a few other places I could give if anyone every comes by Kerala
