The Minnesota Renaissance Festival is probably the coolest, most unique attraction in the Twin Cities Area. It's hard to describe just how fun this place is.
The festival runs August 15th to September 25th. They have a wide variety of foods (Beer Cheese Soup is my personal favorite), entertainment, demonstrations, artisans, etc, etc. It's pretty affordable considering all the entertainment you'll get, the thing that gets you is food, drink, beer...
There are several acts that perform throughout the festival, some notable ones are The Tortuga Twins, Puke and Snot, The Rat Catcher, and of course Jousting. All the shows there are terrific, not to mention the actors working on grounds who are spectacular as well.
The Ren Fest can be great fun for everyone, I never miss a year and I love it every time I go.