Grants.gov is the home of all federal grants. It was established as a governmental resource named the E-Grants Initiative, part of the President's 2002 Fiscal Year Management Agenda to improve government services to the public. The project is sponsored by the U.S. Department of Health and Human Services.
The Indiana Department of Administration maintains a listing of current contract RFP / opportunities, typically with short turn around times.
Formerly Foundation Center and GuideStar, Candid is a full service website for finding funders and RFPs, information on non-profit sponsors, and helpful resources on putting together grant materials.
Other Resources
The SAM.gov domains contain data that has been migrated from legacy federal systems, like FedBizOpps.gov. The domain supports two distinct types of federal awards: acquisition and federal assistance.
Federal Register
Published by the Office of the Federal Register, National Archives and Records Administration (NARA), the Federal Register is the official daily publication for rules, proposed rules, and notices of Federal agencies and organizations, as well as executive orders and other presidential documents. It is updated daily by 6 a.m. and is published Monday through Friday, except Federal holidays.