So my first post was about creative writing notebooks, which I think is probably the most useful prompt source a writer can have at their fingertips. However, there are lots of other very good ways to give you the creative spark when you need it, and here a few that have helped me:
When your stuck, one way to get things going again is to look through old photos. Look for details you haven't noticed before. Look for expressions on peoples faces, and try and remember what was said right before the camera clicked. Here's a photo to get you started.
A statue I saw once in Germany. See what you can do with it.
The news is a good way to find real life plots and characters. Maybe something you hear about in the news is exactly what needs to happen next in your novel. Perhaps there's a detail about someone who committed a crime that is exactly what you need to fill out your antagonist, or even your main character. It depends. Check the news wherever you live, and here are a few big ones that might help:
The New York Times
Google News (a good combobulation of news from all over)
Al Jazeera English (a great source for a different perspective, which is what we writers are looking for, right?)
London Times (stories from our friends across the pond. Always fun.)
Web comics/humor strips
This one is fun. I like these because often they provide poignant glimpses into human nature, not to mention hilarious situations, that may give you back some of the enjoyment you're missing in your writing. Here's some of the ones I like:
MyLifeIsAverage (If you don't know this one, you are missing out, and probably haven't been online since Easter)
A Softer World(Unique and artistic)
xkcd (hilarious and intellectual)
Hope those help. Just remember not to spend more time browsing then you do actually writing.