If you haven't seen it, here's a filmed 'interview' with Conan Doyle talking about how he created Holmes and the doctor who inspired him.
"Conan Doyle on Sherlock Holmes":http://www.youtube.com/watch?v=4eq18U5btcg
Holmes stories are useful in teaching pragmatics and inference, particularly understanding what 'deduction' is (Holmes's inference processes aren't really deductive, but deduction is part of it, which means they have something in common with what we do when working out what other people are trying to tell us)
There are lots of interesting things about the interview, from phonetics to pragmatics for linguists. For students of detective literature, interesting that he refers to Watson as Holmes's 'rather stupid friend'. Agatha Christie's comments (see previous post) and this could form the beginnings of an exploration of Watson and/or Holmes, or detectives and sidekicks in general.
(Personally, I'm not much interested in spiritualism but still fascinating to hear Conan Doyle talking about it towards the end)
B--)