I do not know of any Freeware CAD apps, and have only seen one CAD Shareware evaluation (back in 1995, so most likely it's very hard to find
While not being a Freeware / Shareware app, the Turbosketch and Turbocad apps are inexpensive - $20 to $100.
They are useful, and have a "semi-tough" learning curve.
Visio is also useful for CAD work, but not sure of the price.
Last time I was at Fry's (Electronics), saw AutoSketch for like $99.95 on what I think was a full version.
AutoSketch is made by AutoDesk - the same people who make the well known application "AutoCAD". From what I have heard, it works well for many Electrical drawing tasks.