In the blue navigation bar on the homepage, there is a drop down menu for "Category Search" and "County Search." If you search by category, you can drill down deeper by city, county or challenge funds.
You can also search by nonprofit name in the search bar at the top right of the page. There is also a type-ahead feature and search results will start appearing as soon as you type.
You can also search by which nonprofits have raised their own challenge funds.