I second 3v0's vote for Eagle. I have used ExpressSCH for drawing schematics, and though it works and has a good library, the interface is bland and you can't really do much with it. I really didn't care much for it. Once I started using Eagle, though, I never went back. The interface is very neat and clean, and once you get used to it, it's very easy to use. The libraries are huge, and it also has a lot of special features. You can get the free version here: