default route ospf single area different isp for different locations

[kchurch]

hp 5500's in single area ospf network connecting multiple organizations which have there own isp... the ospf is in a ring topology with the local area networks uplinked to the ospf ring.. what is the best option to have traffic originating from on organizations location to be default routed across ospf ring to the location with their isp connected... not all ips connections are local...