Not really teaching math but this came up in my facebook feed a few months ago -
http://ideas.ted.com/math-101-a-reading-list-for-lifelong-learners/I've now read and loved #3 and #4 (I have some more on hold at the library but it isn't my turn yet). The Ellenburg book might be a great place to start though. It aims to simplify and explain math to everyone. You won't be able to tackle university math problems after just reading it but it might be a foundation of how/why before diving into the more technical details of how from other sources. It is the first book I've read that tries to explain the beauty of math and tries to demystify it if that makes sense.
The 4th one is less about teaching math and more of a history but it might be a good non-STEM gateway to math (or not - I'm a huge STEM geek so maybe that is why I liked it, YMMV...). For me it was kind of the opposite - a STEM person's gateway to history. If nothing else it has been an entertaining read.
Another good read is
http://www.amazon.ca/A-Short-History-Nearly-Everything/dp/0385660049 Again, not exactly a course in the sciences but might be good as background reading. Both DH and I have read it and we did the audio book on a road trip with the kids. DS9 loved it, DD7 was a little less impressed but given their personalities/interests that wasn't completely shocking.
Now off to check out some of the above shows/books. They look amazing!
