There is a vast amount of Internet material on World War I, and any brief search will pull up thousands of hits. Thus, I can only provide links here to some of the sites I have found useful in my research, with the hope that these will be useful as a starting point to your own study.
Major personalities from World War I
provides a list of biographies of many of the important actors from the
war, including Archduke Franz Ferdinand, German Chancellor Bethmann-Hollweg,
German strategist Bismarck, Tsar Nicholas II, Kaiser Wilhelm II, and Sir
Edward Grey. These biographies, though short, are useful background
to an understanding of the events as they came about.
The best website I have found for World War I maps is http://www.dean.usma.edu/history/dhistorymaps/WW1Pages/WW1ToC.htm. Included in the site are maps of the continental divide on the eve of war, the various war plans, the major Western Front battles early in the war, major offensives late in the war (Eastern and Western fronts), and finally, the political realignments of 1919 after the Treaty of Versailles.
Other useful sites for maps include the following:
General links on World War I issues
Timeline: July 1914: the July Crisis, http://www.worldwar1.com/tlplot.htm, provides a day-by-day timeline of the escalation of tensions leading to the outbreak of war in early August. The timeline also provides interesting quotes from the actors who lived out the events as they occurred. As the unidentified author states near the top of the page, the assassination of Archduke Ferdinand "should have been a localized incident" but was turned into a world conflict by certain individuals who used the assassination as a way to carry out their strategic ambitions.
The accompanying Timeline Summary, http://www.worldwar1.com/tlss1914.htm, briefly describes some of the principal causes of the war. The few sentences explaining each of the causes do not provide a substantive look at the reasons for the outbreak of war, but they are enough to get a basic overview of the complexity of the situation.
Another chronology of World War I events can be found at http://www.spartacus.schoolnet.co.uk/FWWchronology.htm.
This site provides a nice list of 100 or so events from the war, with a
link to a few paragraphs describing the events as well as internal links
to other interesting information.