The International Database of the Begoniaceae is online, free and open to the public. It is a work in progress but promises to be a reference resource for all of us who love and grow begonias.
Click on the "Links" tab and check out the begonia societies around the world, plant sources, and seed sources. Then there is the Begonia Links page to peruse with its links to vendors, associations and all things begonia.
One feature of the database's website is the complete reproduction of the book, "Down to Earth with Begonias " by Peter Sharp. It's incredible! I scrolled through some of the pages and can't wait to have time to read it word for word.