It's just a little bit of an understatement to say the Internet has made the work of genealogists a whole lot easier. It conceivably could've taken your grandfather a few years to research five generations of his family tree; now you might be able to do the same thing in a few hours. But there does come a time in every amateur genealogist's life that he or she has to take the plunge and physically find paper records. In these difficult times the Internet will come to your rescue (at least initially) in the form of NUCMC.
NUCMC (the cool genealogists pronounce it "nuck muck") stands for the National United Catalog of Manuscript Collections. It's administered by the Library of Congress, which in 1959 took on the enormous project of documenting the country's history by helping libraries and other groups catalog their manuscript collections. (Manuscripts are unpublished handwritten or typed documents, like personal letters, diaries, business records and family histories.) Since then, more than 1,800 groups have added their collections to the NUCMC, mostly historical societies and libraries — public, academic and special libraries, which usually focus on a single subject, like medicine, law, religion or a certain location.
NUCMC is an amazing resource for genealogists. Because it contains solely unpublished manuscripts, this is information you won't be able to find anywhere else. It holds 1.5 million catalog records that correspond to millions more manuscripts and archival collections from the 1,800 contributing organizations. Until 1993, the NUCMC was available in print form only, and the printed catalogs are still available in 1,400 locations around the country. Starting in 1986 everything was also put online, searchable through the Online Computer Library Center's WorldCat.
So if the manuscripts you're searching for happened to be catalogued by the NUCMC after 1986, you're in luck. You'll be able to see all the information about your documents online. You won't be able to see the originals, but NUCMC will tell you exactly where they are. Then you can contact the organization that has them and figure out how to view the documents — maybe digital files can be emailed. If you don't find what you're looking for, that doesn't mean the documents don't exist — you might just have to do some legwork to track down the printed volumes.
The NUCMC search engine can be a little daunting — it's full of specialized archivist coding and perhaps unfamiliar terms. It's truly a gold mine, though. You can start with the simple search form and work your way up to more complex searches. Once you've figured out the codes, you could easily dig around for days. A search for a great-great-grandmother in the early 1900s might land you her family Bible, complete with a handwritten family tree. Who knows what you'll find!