Word and similar programs are terrible for drawing diagrams - that's not their intended purpose.
So far, I've found that Inkscape works excellent for drawing diagrams. The industry standard, of course, is Cadence (for electrical) and AutoCAD (for mechanical) but they're quite expensive.
What I would like to see is an app for a tablet or similar touchscreen device where I could draw a schematic on it like I do on paper and it would automatically translate the symbols into a nice computer-drawn schematic. (Basically, I want a schematic editor where instead of having to select parts by using a part browser or typing the symbol name, I just draw a symbol and it would try to figure out what I mean.)