Thought I would start a thread about Argyll CMS.
Argyll is a full open source multi platform colour management system.
Windows : http://www.argyllcms.com/downloadwin.html
Mac : http://www.argyllcms.com/downloadmac.html
Linux : http://www.argyllcms.com/downloadlinux.html
This is command line style software, so there is no graphical user interface.
It has many options that are not available with other profiling packages.
Probably the best gamut mapping I have ever used, with many options to improve the conversion from RGB to CMYK, or any colour space.
Options to overwrite the standard rendering intents Abs, Per and Sat tables found inside a standard ICC profile.
This software is not easy to get started, but is well worth the effort.
I have lots of batch file to automate different functions of the software.
Would be happy to share everything with any who wants to learn more about colour management.
But beware, if you just want to make a profile from measurement data, maybe just use a standard package. But if you want to learn what different parts of a ICC profile do and how to get the best out of your printing, it is the best place to start.
So give it a go, and if you have any questions, just reply to the thread.