Inkscape focuses on the SVG format as its primary file format. This highly capable editor has a very good SVG integration, supporting many of the more advanced features that aren’t always available in other apps – such as alpha blending, cloned objects, and markers.
Full support for different colour modes means this is a viable alternative to Illustrator for both print and web design, and although the interface is somewhat simpler than Illustrator, it’s still possible to achieve extremely sophisticated artwork. Of particular note is the ability to trace bitmap images, support for variable width strokes and native import of Illustrator files.
There are source binaries available for Windows, Linux, and Mac, and compiled versions currently offered for Windows and Linux.