Yes: Home School Legal Defemse Association/HSLDA.
Independent chapters in almost every state.
My homeschooling is done, but we maintain our membership with a $100/year gift. The association uses it to support homescholarship for cash-strapped homeschool families; for curriculum and stuff.
Several organizations exist to protect homeschooling. The foremost is the Home School Legal Defense Association (HSLDA). They are involved in both national and local political and legal activity surrounding HS'ing. Most states also have a state association that exists to support, encourage, and be legally and politically active in the respective state. Then you have local support groups. If you do not know where to start, look up HSLDA. They can refer you to a reputable state organization who can then refer you to a reputable local support group. Having done this in two different states, this typically works very well and can quickly get you in contact with other HS'ers.
Your local place of worship can often times be a resource as well.