Back again, now with another tip.
When you don't have a (expensive) photo editor but want to grab colors from webpages or other applications there is this nice little application created for nothing more than that purpose: Sweet Sixteen.
The nice thing of Sweet Sixteen is that it can grab the color for you and immediately converts the color to Hex, Weg-Safe, RGB and HSL.
It is donationware and you can find it here: http://www.crescendosw.com/index.html.
When you want to know about color schemes you can go to adobe kuler at http://kuler.adobe.com/ .
Really great stuff!
To integrate this into the color picker of OS X and, like I did, use it together with Sweet Sixteen so that you can translate the themes into Hex as well, you can use Mondrianum.
You can find Mondrianum at http://www.lithoglyph.com/mondrianum .
Mondrianum is beta software right now and there is no pricing information available (as far as I know) right now.
Have fun...