this depends very much on how complex the drawing is. If it is a simple geometrical object that can be represented with couple of colors at most and it is not necessary for it to be exactly to scale, my recommendation is to use PowerPoint or similar, and "build" the drawing using basic shapes. There are many great drawing tools but most take some effort to learn, and I still find myself reaching for Keynote most often when I have to do simple illustrations. The dirty secret is that many true designers do this as well :).
Getting images out from PowerPoint can sometimes be difficult; if there is an option for "export as image," you might try that, but make sure the quality is good enough for publication (sometimes PP etc. may totally mangle the image with packing algorithms). A trick I use often is to zoom the image in powerpoint/Keynote so that it just fits my screen, and then take a screenshot out of it. That ensures a quick 1980x1200 image, which can then be saved either as PNG or TIFF.
If you can share a sample picture of the type of drawing you are after, I can probably offer more assistance.