Some writers have such well-designed web sites that it would be a pity not to publicise them as much as possible. This is the case of Road Dahl. His website is full of treats. For example, there you can listen to the man himself talking about his craft. Definitely worth a visit.
Also, you can read one of his stories "Beware of the Dog" here.
The British Library has got a fantastic website. I´ve just found out about their literature section where you can read - and listen to - manuscripts by Lewis Carroll, Jane Austen, and other great writers. Also, do not forget to check the online gallery and the site Sounds Familiar. You can listen to different accents and dialects of the UK. This is almost as good as visiting the library in London.
Is it the plot? The language? The resolution? If you want to know more about what makes a good short story, visit this site. You will be able to read "A Jury of Her Peers", by Susan Glaspell and also learn more about the elements of a good story.