Weby Icon Set contains 100 icons at 64×64 pixels and are available in png, ico and icns format.

They are free to use for both personal and commercial projects, including websites, templates & software.

The original post can be read here.

Circular contains more then 100 png icons, 16×16.

The pack is free to use for any purpose you need, personal pr commercial.

This set I guess needs no more presentation.

The version 1.3 contains 1000 free icons for use in personal or commercial projects.

You can download it from here.