Researchers can now access digital images of documents on Internet. This is a growing area of Internet. If you do not find what you need now, check back in a few weeks and it may be there. There are free digitals available as well as those requiring a subscription or pay per image.
Ancestry.com, Ancestry.com, has made images available of census, passenger lists, books and newspapers, to name only a few. This is a subscription database.
Footnote, Fold3.com (formerly Footnote.com), is a fast growing, popular web page with digital images of Revolutionary War pensions, naturalizations, certificates and much more. They are in partnership with the National Archives as a subscription database. Historical newspapers, books and documents can be found at GenealogyBank.com, GenealogyBank. Their records range from historical (1690s) to modern (1970s to current). This is also a subscription database.
A rather unique United Kingdom web page is, findmypast at Find My Past. Family trees can be created and discovered on this web page. Researchers can search over 500 million records in the such areas as vital records and census. The pay options are either by subscription or per view.
The free digital images available on Internet come from a variety of places, one being libraries or archives. One of the largest, on-going projects will be available through the Family History Library in Salt Lake City. They are digitizing microfilm stored in Granite Mountain. These images are being indexed and will eventually be available on Internet.
If you are using the FamilySearch (LDS) web page, FamilySearch International, and discover a notation in the library catalog that a book has been digitized, be sure to click and view the digital images. This will take you to the Family History Archives of Brigham Young University at http://www.lib.buy.edu/fhc/. You can also explore this web page without going through the FamilySearch site. Images of books are usually downloadable in PDF format which requires Adobe Acrobat Reader. Most computers have this feature.
While in the neighborhood check out the HBLL Online Collections at http://contentdm.lib.byu.edu/cdm4/search.php. This contains a list of of collections ranging from dairies, maps, books, and biographies to family histories. They can all be searched at once or specific collections can be searched.
A very good listing of digital library projects can be accessed at Wikipedia at http://en.wikipedia.org/wik/List_of_digital_library_projects. Some of these do not pertain to genealogy. Further information about digitals can be found at Cyndi's List-Primary Sources, Primary Sources. Scroll down to "Online Primary Sources."
There are many archives and historical societies placing digital collections on their web pages. With those collections and the many libraries that include digitals online, it is easy to spend a good deal of time exploring this area of Internet research. Some examples of these free digitals collections can be found at:
Illinois Digital Archives http://www.idaillinois.org
Washington State Digital Archives Washington Secretary of State Sam Reed Digital Archives
The Iowa Heritage Digital Collections http://www.iowaheritage.org/
New York Public Library Digital Gallery http://digitalgallery.nypl.org/nypldigital/
The Digital Collections of IUPUI University Library (Indianapolis city directories)
Even though there are many subscription newspaper collections on Internet, you can also find some that can be searched and browsed for free. The images can be copied to your hard drive for future reference. Examples of these are:
Utah Digital Newspapers http://www.lib.utah.edu/digital/unews/
Colorado Newspaper Collections http://www.cdpheritage.org/
Virginia Gazette http://research.history.org/DigitalLibrary/BrowseVG.cfm
Keep in mind that these are just a few listings of digital images available by subscription, pay per image, or for free. A search using Google, Google, will produce even more. As you learn about more, use them, evaluate the quality of the web page and ease of retrieval. Be sure to share the web page URLs with your genealogy friends.