If you pay enough attention, inspiration can strike you at any time. Sometimes, though, you've got to chase it down. I'm an artist, and sometimes certain sounds or light in the city gives me inspiration to capture it on something: paper, or better yet, canvas... And sometimes I'll have an idea for a piece but I need a visual guide to help me through angles and depth and such... basically all the technical difficulties.
www.corbis.com is a great visual site for pretty much any photograph you can think of, plus you can pick the camera angle and content in two clicks.
And, of course, a muse always helps (hint, hint, wink, wink)
Sarah's style is quite different from mine but we definitely cover the same themes... as long as you're raging on, the rest is icing...
When the jar's all out of candy, don't come blaming me...