GiftedSources.com is a site that contains links to a variety of resources related to gifted education. The links on the left take you to pages with lesson plans, interesting websites, articles, and professional organizations. The site does a nice job of separating lesson plans by subject area, however you have to click on the individual links to find the targeted grade level. This can be cumbersome.
GiftedSources.com is maintained by Kimberly P. Code, Ph.D., an assistant professor at Northern Kentucky University, who has been involved with gifted education for many years. The sites she has chosen are quality, education-approved sites. I especially like that she has links to sites related to The Arts, as they are often forgotten on sites like this.