I am a huge fan of the Kindle and do most of my reading on it these days. I have found this site Pixel of Ink, it is amazing. It lists Free books available on Kindle. I don't know how she manages to compile her list, but it's amazing.
Pixel of Ink also lists highly ranked books under $1 and other good deals available on Kindle.
So what are you waiting for? You can subscribe to Pixel of Ink's email, or like the page on Facebook and start learning about all those free Kindle books you've been missing. They aren't all classics and romance novels.