Simply..
A friend pointed this site out, I believe, a long while ago and I recently re-discovered it and found a great performance by Bon Iver. You will also find performances from other artists as well, but not simply concerts but also special performances like this one from Bon Iver (click the image above to go to that one btw). There are some great videos and moments to be found there so take a few minutes and browse through. I suppose I should note that the site is written in French but sometimes the articles can be found in English as well.
Fantastic.