Anyone aware of the current situation with regard to colour calibration and Linux?
Yes you have support for color profiles through the library lcms (little color management system) that is part of all desktop distributions.
But just as in any operating system the use of it in specific programs differ, but all the important programs for image editing supports it, like Xsane, Gimp or imagemagick. But be aware that fiddling with profiles and colorspaces very often just causes more problems than it solves. Allready a quick look arounf on the net showes what troubbles people dig them self in when they start to hunt some magick bullet in color management. I do not use it normally since i have been lucky to have a screen that i could get right enough by just using xgamma settings in the X-server configuration file and i do not use use anything else than sRGB. Well.. occasionally i enable a scanner profile i have made with a target from Wolf Faust, but this is only for configuration purposes of other things, like when i create medium definitions or deliberately want to scan without any tweaks at all (xsane turns off almost everything regarding colors when enabling color management, like it should - why else enable color management?)
Try to get sRGB to look OK on your screen without profiles if you can. If you succeed in this you have taken the simple road to know that your pictures will look as they should in other computers or on paper from printing services, assuming they also render sRGB like it should.
Look up Argyll CMS and dispcalGUI. Argyll is command line color management and dispcalGUI (display calibration Graphical User Interface) runs Argyll with a GUI. I just got an X-rite EyeOne (i1) to calibrate my screen. It works, but nvidia's driver isn't properly compliant with the linux ecosystem, it has a broken xrandr implementation, so the calibration process hangs. dispcalGUI and Argyll do connect with the EyeOne fine, and I can get a color temperature reading, but the calibration process fails at the xrandr stage when Argyll starts to display calibration color patches.
This is an nvidia driver problem, not a linux OS, Argyll, dispcalGUI, EyeOne, or hardware problem. Who knows if nvidia will do the right thing and write proper drivers?
I have a monitor with button selectable Adobe RGB, sRGB, Custom, emulation, and calibration settings, so I can easily and quickly change color spaces/calibration. sRGB works fine for web previewing with factory defaults.