I was buying tickets today for the behind-the-scenes tour of the Eiffel Tower, when I noticed a field for a coupon code. A quick google search found me this site
Clicking on "cultival" (the people selling the tours on behalf of the Eiffel Tower) yielded this code EDENRED201210
it worked to get me 10% off my tickets. The code is good until June 30.
Yes, I'm cheap. If I see a field for a coupon code, I can't not search for one ;-)