Ubuntu 9.10 Karmic Koala icon theme available for download
You can also install the icon set by opening a terminal and typing (without quotes): "sudo apt-get install humanity-icon-theme".
The new set includes icons for actions, animations, applications, devices, categories, and a whole slew of other areas.
The entire icon set weighs in at 1.4MB and each icon is saved in Scalable Vector format which means the icons should look good in a variety of resolutions. You can read more about the new icons at the Ubuntu Wiki.
[via Ubuntu Mini]