Listed below are some agency links that I have found useful and that may assist you in your search for external funding opportunities. If you know of a really good site that is not included here, send me a message and I'll check it out.
Grants.gov - Single portal for over 900 grant programs offered by the 26 Federal grant-making agencies. Includes capabilities for searching and applying for federal grants.
Kansas Funding Resources for PRIDE Communities - Provides links to other State granting agencies.
National Academy of Sciences - This also includes National Academy of Engineering, Institute of Medicine, and National Research Council