Public Domain Vectors
A wonderful directory of public domain images and illustrations. There is a good search function, and even web-based tools for creating and editing SVG files.
“Vector images provided via download on publicdomainvectors.org are bound to Creative Commons Deed CC0. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission. Although absolutely not required, a link back to Public domain vectors is always welcome.”