Obituaries are a great resource of information, whether going up the tree or down. A good obit lists the birth date, death date, parents' names, and, if it is really fabulous, even a marriage date.
When I am looking at an obituary, I try to pull every piece of information I can from it, from sibling names, to children and sometimes, if I am lucky, grandchildren.
The obituaries I am focusing on now all come from Crawford County, Missouri. My maternal grandfather's family has lived there for many generations. In fact, the Andrews family (from North Carolina), the Martins (from Casey County, Kentucky and before that Albemarle, Virginia), and the DeWeeese family (from Cumberland County, Kentucky) all settled in Crawford County at some point before 1850. The Davis family, though, has been there the longest. They first settled in Crawford County on Whittenburg Creek in 1832.
Generation after generation of these families have stayed. I still have first cousins (granted, once removed) who still live in Crawford. So, when I go through the obituaries, I merely do a search of my tree to see if I'm related to any of the people listed in the obituaries. More times than not, I am.
Currently I have gone through all the obits from 2000 through half of 2001. My plan is to catch up and go through all of the obits, including the current ones. Luckily for me, the GenWeb site for Crawford County has all of these obituaries online. What a fantastic resource!