NSPIRES -NASA research opportunities
National Endowment for the Arts
NEA - Homepage
National Endowment for the Humanities
NEH - Grant Programs and Deadlines
NEH RSS Feed - updates on all NEH programs
National Institutes of Health
OER -Office of Extramural Research - NIH Funding Opportunities/Notices
NIH eRACommons "LikeThis" - posted 8/9/12
"A thesaurus-based search tool that allows you to find similar funded projects and publications. You can enter scientific text or select one of your assigned projects to retrieve a listing of similar funded projects and/or publications. In addition, a list of scientific terms with synonyms and scaled weights is generated based off of your scientific text. You can enter scientific text or select one of your projects to retrieve a listing of similar funded projects and/or publications."
This website lists all the government spending including grants by state, agency and topic. It's a great resource to locate where to apply and obtain a successful proposal.