I needed to do some vector drawing, and after getting frustrated with Powerpoint I searched for free vector drawing applications. The first hit was Inkscape. It turned out to be surprisingly good, and filled my needs very well.
Surely Inkscape is not without flaws: It crashed once and the printouts of drawings contained a lot of extra lines, but I had happened to save just before the crash, and saving the drawing as a PNG image worked fine, so the bugs weren't showstoppers for me.
For a free/open source software Inkscape seems to be also relatively easy and intuitive to use. I recommend.