Ideas for what? Hubs?
Lots of places. I look through the questions to see what people are asking about. I read hubs in areas I am interested in and sometimes an idea for a different slant on something comes to me. Other question sites on the internet are a source of ideas. I also look through google key words tool to see what people are searching for.
In terms of ideas "coming" to me, I think sometimes you just have to sit (or lie) still, doing absolutely nothing. No radio, no tv, no computer, no books, nobody talking to you - just letting your mind wander. It was easier when I was younger, daydreaming doesn't seem to be as easy these days :( but when nothing is distracting you and you just let your mind wander where it wills, some pretty good ideas (or solutions to problems that have been bothering you for a while) can just pop into your head.
You can do this deliberately just before bed time. If you have a problem to solve, then have a think about it, looking at all angles, without stressing out over it. Then put a pencil and paper beside your bed and put the problem right out of your mind. Tell yourself that you will have a solution to it in the morning and relax and go to sleep. (Just telling yourself that you will have a solution can help to de-stress you if the problem has really been worrying you.) In the morning, you should have an idea about how you can solve it, or at least move it forward. The paper and pen is if you wake up in the night with a sudden blinding flash of inspiration, so you can write it down and not forget it - believe me, that can happen!