SVG-edit is a surprisingly powerful in-browser vector image editor
Watch out, Inkscape! As Web browsers become increasingly powerful, it is only a matter of time until a free browser-based vector graphics editor pops up that is powerful enough to compete with a desktop application -- and SVG-edit may well become that editor. Currently in version 2.5, this open-source project was surprisingly responsive and powerful on my aging Firefox 3.6.8.
The one thing I couldn't get it to do was curves. The feature list does say that it supports "curved paths," but I couldn't figure it out, despite previously having worked with Inkscape, CorelDRAW, and Illustrator. Other than that, SVG-Edit gracefully handled just about anything that I could come up with. You can change opacity, set the fill or the outline to any solid color or gradient, align items on the canvas, shift Z-order (bring items to the foreground or send them to the background), and lots of other functions. In case you're wondering, that screenshot isn't blurry -- it's showcasing SVG-edit's built-in Gaussian blur functionality.
One neat thing that you can do with SVG-edit that you can't do with other apps is resize the UI. When you use your browser's zoom functionality, the whole thing grows, including the buttons. And it all stays crisp, because the buttons use SVG icons. It's beautiful work.