WordCamp US is coming up soon in Philadelphia and it's going to be a special event.
WordCamp US is the first time that the WordPress community has really tried to hold a large conference along the lines of DrupalCon and PyCon. They're expecting 2,000 attendees in Philly.
It certainly helps to increase attendance when tickets are an absurdly low $40 for 2 days. Conferences like this normally cost from $300 to $2000. There are still tickets on sale today. If you can't make it in person, you can buy a livestream ticket for only $10.