It's hard to overstate the value of the FamilySearch county wikis for US research. In the last few years, they have improved them from bare stubs to detailed articles with numerous links and sources and the locations of many record types. If you last looked at them a while back, you need to check back.
For example, in Jefferson County, Nebr., it tells you that the county clerk has marriage records from 1864 and that the county judge has probate records from 1870. It gives a link to a site for Nebraska newspapers and for county cemeteries. It gives you the address and e-mail for the county genealogy society and the public library. It describes county boundary changes and known record losses and has a table with the county population in each census. You can do a lot of research from home using its links, and it lets you know which courthouse office to visit for each record type when you make a genealogy visit.
Don't miss this resource.