There is hardware calibration available for Linux, if you can find the hardware to do so. The Sp*der 1 and 2 are allegedly supported. The Sp*der 3 maybe.
Here is an article on using the Pantone Huey (another inexpensive device that is actually supported on Linux). The X-Rite Eye-One Display is also supposedly supported, but can find no instructive links, though this one is positive.
This topic is not simple and cannot be summarized in a single posting easily. Here are a couple of useful links on hardware calibration with the Sp*der and ArgyllCMS.
The Linux Photography blog also has this article on dispcalGUI here.