The NIH has announcedthat it will now allow Investigators to cite their interim research products (Preprints, software etc) in Progress Reports, Grant Applications, and Proposals.
The NIH recommends that Investigators use pre-print repositories that are robust and allow the pre-prints to be easily findable, accessible, interoperable and reusable.
A good example of such a repository is biorxiv.org
For more information the NIH guidance can be found here
Reporting Preprints and Other Interim Research Products