An update today brings a darker color for the default icons in Ubuntu 10.04 Lucid Lynx:
The Humanity Icon Theme got a really nice update in Ubuntu Lucid today which brings integration with the new branding (purple that is) as well as a new Banshee monochrome icon for the panel.
The Humanitarian toolbar icons are some great icons you can use with the Humanity theme in Ubuntu Karmic.
It appears the Humanity Panel Icons Pack has been updated, and now you can simply run a script to install all the icons (I wasn't awate of this, thanks rkv!).