They can be a place to pickup offbeat stories. The Yellow Pages often hold stories just waiting to be told. Burke related a story of a local company that makes the large, novelty-shaped hot air balloons. Being online is also important in getting work. It's all been through email.
Television is another source.
Of course no research would be complete without a visit to the local library. This reference book is also a good way to find association magazines. These magazines are put out by groups for their memberships and are not available on the newsstand. The pay is better than newsstand magazines. Ask for a copy and follow them.