What do they need a grant for? That makes a big difference in where to start looking. I went to a grant writing class earlier this year and learned a lot that I didn't have a clue about.
There are federal, state, private and public grants. A good resource is a local college. Often they have access to the "big" lists.
Cities usually have access to Federal/State Community Block Grants (depends on the project) In our state they are administered throught the Department of Revenue. Often times these are monetary grants that require in kind donations, such as labor, etc. Google community block grants for your state. See what you get. :o)
Have you guys ran into any grants that for profit entities can apply for? Our small grocery store needs a new freezer for ice cream and a cooler for dairy products. Would they qualify for the energy efficiency grants?