The "digitalcolor meter.app" on OSX lost one feature which made it useful for me as a web developer which is accessing HEX values.
Until this morning I put it down to an annoyance that I would have to deal with. Jump in Google and this point and I found out there is away around through plugins for the Colour Picker (I didn't even know you could build plugins for it).
If you are on Lion check out the following two links (in order) Color Picker for OS X and Hex Color Picker
As a part of the system colour picker it also means you can leverage these new features within the OSX apps aswell.
As an extra note, if you are a fan of Adobe Kuler then check out Mondrianum , another Colour Picker plugin, this one adds the color themes of the kuler community