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The official site of the Nobel Prize has extensive entries about each of its winners. Hemingway's includes a full bibliography of his work, a biography, and the text of the speeches given by and about him when he won the prize in 1954.
This is the online gathering place for serious Hemingway scholars. Like, really serious. If you're not planning to spend spring break at a Hemingway conference, you should probably visit another site first.
This site has essays related to the various places associated with Ernest Hemingway. Some are good, some are not so great. Still, a fun place to read up on one of literature's most entertaining travelers.
Okay, this is kind of cool. The good folks at PBS put together this site where you can click on icons representing different stages of Hemingway's life and all sorts of multimedia comes up, from audio clips of Hemingway reading to his favorite recipes. Fun!
You have to visit the library in Boston to gain access to the full collection, but this site has some good online resources useful for those doing Hemingway-related research.
This is also kind of fun. This site lets you jump to different events in Hemingway's life and provides details for some things that other biographies mention only fleetingly. It has the same collective editing policy as Wikipedia, however, so double check facts with other sources.