Inkscape
I've been playing with Inkscape, a vector graphics editor. It's really quite easy to work with. Here's a couple images I've made. I converted them to PNG images, mostly because I don't know whether IE actually supports scalable vector graphics (SVG) images.
This first spirally thing is actually the first image I made. I was just playing around with some tools to see what they actually do and happened across both transparency and blur.
This next image was the next I tried, and though it took me a while to figure out the handle, I think it turned out really well.
