We host several collections of free (CC-BY) icons at toicon.com. It's pretty popular among our UX designer friends as a more selective alternative to the Noun Project.

Today, we allow download of SVG files, and to appease Adobe Illustrator we have to actually process the files to move styles (pretty much just fill colors) from a central <style> element to individual style attributes on each <path>. This works well enough for Illustrator, but complicates using CSS to adjust them in when embedding the SVG into HTML.

Our current plan is to make downloads include both "designer friendly" (as above) and "developer friendly" (with the abstracted <style>). I'd love input from people here, though, about what style of SVG styling is most useful!