If you're looking for a third option association this year, here's a list from the SC State Department of Education:
Carolina Homeschooler will soon be added to the list since we're providing services for the 2013-14 school year.
I would recommend visiting the websites of each association listed to see which ones offer the services you need. Narrow your list down to three, then email those three with specific questions to make sure it's a good fit for your family. Then choose the one that rises to the top of your list.