I've not been to any festivals outside the US, but have been to several in Washington state, and also here in Kansas.

Mudjack, do you camp? Do you like bluegrass/country/old timey music? Check out the Mt. St. Helen's festival if you do. There's a camping fee, but if I remember correctly, the jams are free--and there're a lot of jams. We had a great time when we attended. I agree, Folklife is a blast, but the crowds always wore me down... interesting stuff, though, huh?

In Kansas, the Winfield Music Festival is the biggie, of course--definitely not free, but incredibly free-spirited. Non-stop jamming, visiting, listening, and kicking back, 24 hours a day. Fantastic! Two huge campgrounds. Great performers, if you've a mind to sit and listen for a bit at one of the five stages. Great jams, if you've a mind to lug your guitar, bass, harmonica, accordian, bodhran, whatever around the campgrounds for a while. And many, many friendly people enjoying all kinds of music. Highly recommended!