Well, how much in depth are you interested in getting?  I started reading Categories for the Working Mathematician a couple of months ago, and while it sometimes takes a bit of work it's a very good introduction.  The only caution I have is that if you don't have that strong of a math background, or hadn't done it in a few years (like myself), you may have to lookup a lot of definitions in order to understand his examples.  Wikipedia usually provides enough of a detailed description that you can get the point.