There's a thread on Dragonsfoot about an alternative XP system, advancing everyone at the same rate, with an idea of leveling up every four sessions (or whatever you decide,) instead of calculating XP after every encounter. One of the suggested benefits is that players get rewarded for what they want to do, even if "what they want to do" would not normally earn XP (like the example of engaging in politics at a goblin carnival.) There was also a couple blog posts a long while back about XP awards for travel, to encourage players to try new locales.
It occurred to me that the the system I suggested a while back of offering XP equal to one of the character's six ability scores would work for cases like the carnival or overland travel, even if no roll was involved. Just decide which ability (or abilities) the characters are using and award that much experience just for participating, plus extra experience for specific actions.
Politics at a goblin carnival? Figure each character gets XP equal to their Charisma, plus XP equal to Strength for attempting to impress someone at the tug of war contest, plus 100 XP per HD for defeating a goblin politically.
Travel over arduous mountains? XP equal to Strength + Constitution every day, plus Dexterity and Intelligence if you hunt for your own game in the wilderness. Braving the rapids to cross a river might be worth a separate 10 times Strength XP award.
Players decide not to adventure and hang out at the tavern every session instead? XP equal to Constitution, plus XP for defeating bar patrons in brawls. XP equal to Dexterity if you play darts; 1 XP per coin if you win a bet. Kinda boring for some of us, and it's slow going, but if that's what the players want, it can be done.