I was recently looking for a favicon of a flag to use in a project I am working on. During my search I came across favicon.cc, a cool little site that lets you design your favicon online, share your creations, and use favicons others have created.
It really is a simple tool, but a genius concept. Sometimes I am looking to incorporate a logo into a favicon, but other times I am just wanting a favicon that reflects the site, and for this purpose this is great! There is quite a growing selection of favicons on there and it will only grow over time.
I have recommended the Dynamic Drive favicon generator in the past for converting images into favicons, but for creating from scratch or picking from a library this site is great!