Well, I have very vivid dreams and more often than not I remember them when I wake up. I can dream whole plot lines. When I was stuck on a plot of a recent book I was writing I would read where I'd got to in the story just before I went to bed and somehow when I woke up I had a vague storyline. Granted I think the story probably needs a lot more work and maybe a lot more sleep.
This happens when I read other peoples books too mind you. If the characters are built up so clearly they sneak into my dreams... so Nicky, Selena is a culprit.