Here are my discoveries, not sure if they've been mentioned but oh well if they have :)
If you have a bonfire sims can do a bonfire dance.
If you take a vacation each destination has it's own dance which you can learn at any lot with a stereo when the locals dance.
At takemizu village your sim can learn Tai Chi from the locals.
If your sims are engaged they can book a honeymoon than get married and the cab will come get them but careful if your throwing a wedding party though cause the cab will come the moment your sims tie the knot.
I did see mention of santa but thought i'd mention father time is in-game as well, if you throw a new year's party father time will come.
If you take pictures while on vacation or just in the neighborhood you can order a photo album or a print to have in your sims home.