A collection of single color SVG logos.
svg
logomono project
Elastic SVG Elements
This site provides a wealth of great SVG demos
SVG Logos
A large collection of optimized SVG logos. Handy.
About those vector icons
The most comprehensive explanation as to why we still use raster icons instead of vector, and why SVG is not the answer.
NounProject
A beautiful, constantly expanding set of free icons. I wish there was an obvious method to download all icons at once.