One series of articles which might serve as a start is Steven Strogatz's series which ran in the NY Times earlier this year:

http://topics.nytimes.com/top/opinion/series/steven_strogatz...

It's written for a layperson (he starts with counting on Sesame Street) but nonetheless touches on some very advanced topics, and describes them in simple ways. It won't give you a firm foundation in mathematics (the articles are pretty short, and there are only 15 or so), but it might serve as a guide for which subtopics in particular pique your interest, and there are numerous references and suggestions for further reading. I believe he's collecting the articles in a longer book, hoping to publish it in 2012.