These are the places we've had birthdays.
Discovery Zone
Chuck E. Cheese
Children's Museum
The Zoo-included cake and admission to zoo
Ben and Jerry's (a 4th or 5th birthday would be better than a 6th, though)-they made ice cream and played games, tie dyed tshirts, too.
Have hired magician for birthday at home -very good, but I wouldn't do it again.
Bowling Alley that also has Laser Tag, bumper cars and simulator rides )-that was a favorite
Little Gym-kidsliked it A LOT. 6 or 7 would be limit, though, i think--for interest. Downside was kids didn't interact with eachother. The little gym staff had them SO organized, that they were CONSTANTLY doing something. But, they weren't bored.
This year, though, I'm cutting costs. .. my son's bday is next month, and I still haven't decided what we're doing, yet. We belong to a club, though, that has an indoor pool and I think they do birthday parties. Since we're members, maybe that cost won't be too bad.