Social Set Pieces in Campaigns

Although mapping and exploring and figuring and fighting are all lots of fun, the best campaigns also mix in a different kind of action in a less dangerous social setting. I've been doing this in all my campaigns, and noticing a spectrum of the kind of interludes I run. Most of them are heavily improvised with the help of various tables, player input, and off-the-cuff inventions. Many of them stem from the carousing and gourmandising rules, or from attempts to buy services or sell loot. Some are just generated as random encounters.

1. The expository set piece. Sometime's there's just sheer fun in kicking back and entertaining the players. You might play this out as the characters watching a religious ritual that explains a mythic story, a procession in which the major social forces in a city each represent themselves, an overheard gossip conversation between two washerwomen. In my Trossley campaign this role was played by the gourmandising feast of the henchman Cordoon. In the current Kaserolle epic I spent a good half hour relating the rhyming play performed by a troupe of traveling players that was commenting on the current action and giving intimations of connections to larger events ... somewhat inspired by Gene Wolfe's similar use of a theater troupe in the Book of the New Sun.
2. The interactive set piece. Here, there is more of a conversation, although the interaction is not exactly free; it follows set rules or is bound by an interrupting event. Your players might be wagering with the patrons on either side as they watch a horse race, conversing with the other passengers as a ferry barge glides past the main sights of a river city, discussing all the reasons why the long-winded merchant should buy their carpet for fifty silvers as he lists all the reasons why only forty will do. In Trossley the players had their individual questions for the lammasu Saheedra; in Kaserolle last week a gourmandising session turned into a feast at a cheese restaurant that alternated conversational opportunities with several NPCs and lavish descriptions of the courses of the meal.

In short, I find it good to have a structure of some kind for audiences and parties so that the players make every word count and the event doesn't drag or fade.

3. The fully gamified set piece. I hadn't really done anything like this before today in the Kaserolle campaign. It's a set piece where the players not only interact but take part with their own mini-game. Imagine a conversation over a card game, for example, gamed out with actual cards, where the NPC grow more generous or cranky as they win or lose. In Trossley a carousing attempt led to a short knife fight and an enemy made. This time I spiced up a carouse table with  ... well, I'll really have to wait for the photos to get to me to really do it justice. This was unbelievable, one of the best times I've ever had at the table and with the full input and cooperation of the players.

Does anyone else find room for set pieces in their campaigns? What kind of techniques do you use to keep them moving along?