While I have not traded the film reader or trip to the library with databases on Ancestry.com and FamilySearch, they have certainly replaced most of the activity and shortened the time spent in locating an ancestor. Libraries and archives close at a descent hour in the afternoon or evening. My computer and databases are on and available 24 hours a day.
The wonder of digital images allows us to stay home and look at an actual image on our computer monitor. There are documents, photographs, newspapers, microfilm and books that are available free. You can opt to read them online or download them in jpg or pdf format to your hard drive.
Digital wonders exist at FamilySearch FamilySearch International. By the day and week there are more images and indexes available. When using the Family History Library Catalog https://www.familysearch.org/#form=catalog on the web site, you can readily see what is available in digital format. Under the title there will be "availability" which indicates digital images or microfilm at Family History Centers.
You can also search for digital images at the Family History Archives http://www.lib.buy.edu/fhc/index.php. This is a collection of published genealogy and family history books in digital format. They come from the collections of the FamilySearch Family History Library, the Houston Public Library - Clayton Library Center for Genealogical Research, the Mid-Continent Public Library - Midwest Genealogy Center, the Allen County Public Library, the BYU Harold B. Lee Library, the BYU Hawaii Joseph F. Smith Library and the Church of Jesus Christ of Latter-day Saints Church History Library. Be sure to search by titles, surname, author or location. There is also an advanced search option. The books can be saved in pdf format.
Internet Archive Internet Archive is a must use web site for finding books and digital images of microfilm. They are building a digital library of Internet sites and other cultural artifacts in digital form. This is provided free to researchers, historians, scholars, and the general public. It is like one big library at your finger tips!
If it is your first time at Internet Archive, the home page can be confusing. In the search box enter your criteria. You can select the media type or leave it at "all media types." Enter a location, type of record, surname ... such as "Iowa cemeteries."
DonsList Finding Guides http://www.donslist.net/PGHLookups/GuidesM.htm provides navigation help with Internet Archive. There are categories, such as directories, institutions, yearbooks, census, military and offsite collections. Digitals from the originals, such as census, can be read online or downloaded in pdf format.
Microfilm records from the National Archives were placed on Internet Archive by the Allen County Library Genealogy Center. If you want to download all of the 1790 US Census (or other years), it is available on Internet Archive. Keep in mind that these are extremely large pdf files and will take up valuable hard drive space.
Also available are War of 1812 Military Bounty Land Warrants 1815-1858, Microfilm Publication M848 from the National Archives. There are 15 reels subdivided into pages. Other military records include Revolutionary War, Civil War, Spanish American War, and some World War I and World War II records.
There are city directories available for many locations, such as the 1799 Hartford, Connecticut or the 1920 San Francisco. These also include area phone directories.
Add to the list of places to locate digital books, one of our favorites, Google Books http://www.books.google.com. If you locate a book that has not been digitized at Google Books, check for it at Internet Archive or DonsList Finding Guides. Google Books have various ways to review their books, such as snippet, preview or read. Those marked "read" can be downloaded.
These are all growing areas on Internet. You need to return often and look for additions. Allocate plenty of time, because you can easily spend hours browsing through the digitals that are available.