Good tools for drawing schematics
Try KiCAD. Now it even does SPICE simulations, ngspice specifically, and it handles pretty much everything else. Other than that, if you wish, KiCAD has also the tools to design printed circuit boards, and even has a 3D viewer and exporter for the boards!
KiCAD runs on Windows, Linux and Apple OS X.
There is also a project called ESIM that bundles KiCAD with a SPICE simulator and differential equation solver.