Here are a few online resources that have been helpful to me in circus. If you have other resources (circus specific or could relate to circus in any way), please send them my way!
Mike D is "a teacher, coach and strength & conditioning professional dedicated to helping circus artist-athletes of all levels move better and train smarter while they get stronger." He runs an online training program and blog around functional strength and conditioning specific to circus, and has blog topics on everything imaginable.
Ken Young's Page of Circus Links
Though I'm not sure how updated this website is, this is an incredible resource for circus links.
Adventures in Aerial Artistry
Want to know what life in the traveling circus is like? Check out Rebecca Ostroff's blog as she tours with the circus!
Circus Talk is a professional social network and marketplace for the international circus community.
Dr. Jennifer Crane is a physical therapist, athletic trainer, board certified orthopedic specialist, and published author. She has been a sports medicine professional for eight years, and has worked with a wide variety of athletes and performing artists throughout that time. Check out her blog for some incredible circus body knowledge.