Browse the agency's website for information on your topic. Most pages will have their own search option or an A to Z list of their activities or projects.
Tip: you can limit a Google search to a particular site by formatting a search lik this:
site:URL of government site AND topic
Example: site:usda.gov hunger -- This Google search will show you results matching "hunger" on the USDA website
You can also search USA.gov or use the SearchGov.com site, which will limit your results to those in the .gov domain.