Why would you want dwarves to spend more time doing things that aren't working?
They wouldn't, they'd just do more things when they aren't working.
A few ideas:
Sports and games: Require equipment (randomly generated when the game is), a few dwarves will organise themselves into teams or something depending on the game. Depending on the game, some skills might be trained. Examples: Chess/Go/Whatever (requires game board, trains Concentration), Hammer Throwing (requires at least one hammer, trains Throwing, may be dangerous for bystanders), some kind of game involving staying on top of a barrel for the longest (requires a barrel, trains Wrestling and perhaps other skills).
Recreational work: Pastimes that are actually work the dwarf gets paid for (once the economy is in again), unless he keeps the results for himself. Examples: Fishing, hunting, certain crafts, animal husbandry.
Storytelling: Find a bunch of other idlers or kids, and tell them tales. Depending on the story, can pass on skills.
Hiking: Probably only done whilst on break. A dwarf grabs a spare backpack and waterskin and wanders around for a while, as far from civilization as they can. On the orders screen, you can disable hikes.
And that's about all I can think of without implementing some really new stuff. All of these should have good thoughts with them--for instance, someone playing a game would get a good thought from that, alongside a smaller bad thought for losing and a good thought for winning.