Online Registration is at RunSignUp.com and go-greenevents.com. If you're a GTC member, make sure to use RunSignUp to receive your automatic member discount. Otherwise, it's your choice. RunSignUp has some extra bells and whistles and go-greenevents is a local company - either one will get the job done. Note: If you have a promo code or coupon code, you will enter it LAST THING at RunSignUp and FIRST THING at go-greenevents.