As you know I work for a company where I run laser engravers. For things to engrave correctly they need to be in a vectorized format. Vectors are images that can be scaled to any size and remain clean, not pixelated. Here is a list of sites I use regularly to get good artwork:
Dafont</a> - not technically a vector site, but the fonts on it are all vector images. Good place to get fonts and pictures.
Brands of the World - has a ton of copyrighted logos. Everything from Nintendo to Nike.
Vectorportal - kinda sucks, but sometimes has good random pics.
If you have any more please feel free to submit to them.