The National Science Policy Network has a good Q&A site where credentialed scientists answer public questions about their subject area. I forget the URL but a google search should turn it up in a few pages.
There's a similar one called the Science Creative Exchange where scientists sign up to talk to writers in hollywood and work through scripts and make the science in fiction more accurate wherever possible.
I love both of these and have spent lots of time on them in my (ever dwindling) free time. But I'm also the guy who's commenting on a HN post when I should be studying for the biggest exam in my career (USMLE Step 1), so I'm not the best example.