I've personally never used anything other than Photoshop. It does appear Gimp does support color management, though I have no experience with how they have it implemented. Affinity Color is another app that a lot of people are using if they opt not to use Photoshop. If you're going to get involved with color management, it's kind of assumed you're going to use something more than a free or built in Windows image viewer. If you want to get your hands really dirty, there are some code bases you can use to apply ICC profiles here:
http://www.color.org/opensource.xalter
Personally, I would just use PS or the like and be done with it. There are a number of viewers that read embedded color profiles, but you need a full color management engine if you want to do anything more than just apply a profile.