If you're an Adobe kuler user, you need try out this cool Color Picker add-on — Mondrianum.
While kuler membership is not necessary to run this add on, unfortunately the beta only runs on Leopard — another reason to upgrade.
Apple Color Picker is available in more Mac OS X applications, including Photoshop. In PS you just need to switch from the Adobe picker in General Preferences.
Mondrianum adds another way to pick colors besides the already default 5 other ways, such as color circle, sliders, swatches, image and crayons.
Mondrianum downloads color sets right from kuler using tags or you can select from the popular, highest rated and newest color sets.
Tag search means if you come up with a unique tag and share it with your friends you can effectively share color sets across multiple work stations.
Here are a couple of tag searches and their results: