The National Association for Gifted Children (NAGC) web page is a great resource for parents of gifted children. At the home page, click on the "Parents" tab at the top, and you will find articles on parenting and educating gifted children.
You may also be interested in the Resource Directory, as it provides hundreds of programs and suppliers for resources for gifted students.
You may also be interested in joining NAGC as a parent member. With membership, you will receive their magazine, Parenting for High Potential.
Finally, take a look at Resources for Parents, where you will find a glossary of terms, the NAGC Gifted Program Standards, a parent toolkit, and more.