Impact statements describe the institutional context for your research and explain the likely positive effects of grant funding. Some sponsors require you to include this information in a specific section of the proposal. Others don't, but including this information in a proposal will generally strengthen it, so consider mining these documents when writing any proposal. For NSF and NIH, they should be used as templates on which to base your own individualized statement. They aren't intended to be used verbatim.
Middlebury's impact statements are updated annually, usually at the end of the spring semester. If your deadline falls around that time, check with the Sponsored Research Office to be sure you have the most current version.
Proposals submitted to the National Science Foundation's RUI funding mechanism must include an impact statement. This template is organized to meet NSF's requirements and includes the institutional information you need to construct a compelling statement.
Applications for the National Institutes of Health's Academic Research Enhancement Award must include an impact statement. This template is organized according to the AREA guidelines and includes a specific statement about graduation rates in the health-related sciences that is required by this program.