I tend to prefer regular CAD programs for that, but then you have to build a "library" of schematic parts.
That being said, Google Sketchup is pretty damn good. I have Sketchup Pro, as I dabble in 3D.

Here are a couple of other choices, that I have heard about, but not used:

http://sourceforge.net/apps/mediawik...?title=TinyCAD

http://www.expresspcb.com/expresspcbhtm/download.htm