The U.S. House of Representatives has approved a bill (unanimously!) to strike the words "mental retardation" and "mentally retarded" from many Federal statutes, replacing those terms with the words "intellectual disability" and "individual with an intellectual disability." Read the full text of the bill here.
Within the context of special education laws, the bill will mean that wherever "mental retardation" is referred to (for example, when discussing eligibility categories), that term will be stricken and replaced with "intellectual disability." The same applies to section 504 of the Rehabilitation Act.
The law is called "Rosa's law" and is named for a child with Down Syndrome from Maryland. You can read about Rosa's story, including the inspirational testimony of her brother Nick in a hearing before representatives of the Maryland General Assembly, in this press release from Senator Barbara Mikulski's office, or in ABC News' story about the law and the family that inspired it.
This is only one step, albeit an important one, among many that will be needed to stop the R word. Changing the designation in laws may not stop the use of the R word as a derogatory slang or insult, but it is certainly a step in the right direction in terms of societal awareness.