Smiling and safely being sexy, as that thing on her hip is a condom. Source: Sex and Submission.
What better way to start a weekend than with a whole trove of happy people engaging in sexual bondage? My flying monkeys brought in a clue, in the form of this post on Fleshbot, entitled "Bondage is Joy" showing a couple of naked, bound women laughing their asses off, and why should they not? Check it out!
Maybe her foot is being tickled as the ropes are applied, but there's little doubt she's having fun. Source: Hogtied.com.
I did a little more research and found the mother lode, however, the Happy BDSM Archive. It's a tumblr full of images of bondage models and amateurs engaging in bondage and so forth, mostly bondage, grinning like fools while they're at it. It's mostly women in bondage, but there are some men in bondage, so if that squicks you, be sure and take a good look at the thumbnail before you click on it. Basically however, this is the biggest trove of silly-ass grinning bondage fans I know of.
None of the photos in this post are from the Happy BDSM tumblr archive, they're from the good folks at Kink.com. Lot of grinning people there, too. Source: This one is also from Hogtied.com.
So enjoy the happy bondagers, and have a great holiday weekend!