I LOVE me a huge gathering...expensive sometimes but great none the less.
Lets see...
Been to Bonnaroo a whole bunch of times
Lollapolooza a few times but that was back in the 90's when they still toured
Attended Burningman...I think around 2004, 2005ish
Mardi Gras...well that's a must
New Orleans Jazz fest many, MANY times (Going again this year)
County Bluegrass festival in Limestone, ME
CMA Country Music Fest...not really a country music fan but the atmosphere in downtown Nashville is INSANE, specially after dark when the tourists start heading off for the night.
Riverbend Music Fest in Chattanooga
Tennessee Cigar and Brew Fest is pretty cool
Murfreesboro Jazzfest is always fun to catch and sometimes play....
...I know I'm leaving a whole bunch out too...
Anyway any excuse for a good time!
EDIT: Jeez heck how could I forget one of my all time favs Telluride Bluegrass Festival! Great show in a great town.