One of my stock responses is that there are no new ideas, only new ways of telling the story. I find it very freeing to accept that pretty much every plot has already been done countless times before. It means I can focus on the things that really draw people to a book; the characters, their relationships, the reasons the reader should care.
When I get a new book idea, it most often starts off with an idea for a good scene, or an interesting relationship. The most common source of ideas is a new song or piece of music. I'll think of a scene or story that suits the piece and before I know it I've added another entry to my folder of book ideas. My list currently stands at around 35 individual books, both adult and YA, fantasy, urban fantasy, and some science fiction.
My most recent idea is for a science fiction space opera I got from this song:
I'll probably leave this one on the backburner for a while. My sci-fi tastes tend more towards pulp action over hard science, so I'd rather make sure I can either pull that off or I've learned enough to make the science believable enough that it doesn't get in the way of the fiction.
Where do you get ideas from? What do you think about the concept that there are no new plotlines or ideas?