Wow, what a great question!
I suppose for me, the main way I've introduced people to Narnia is through my blog. I frequently write about things that first come up here at NarniaWeb, things that would take paragraphs worth of text to do justice - like my "top 5 Narnia performances", thoughts about Netflix's upcoming Narnia content, etc. I occasionally get a comment from a NarniaWebber, but most of my (admittedly few) readers are not as into Narnia as me, so I'd like to think I help them go "further up and further in".
But most recently, I introduced a friend to the books beyond LWW. She's a huge Harry Potter fan, and she got me into it last year. So after I had seen all the movies, I surprised her with a crazy blog post where I did the classic "who would win in a fight" scenario. She and other readers liked it so much that I did a second post this year. But this year I brought in a ton of characters like the Lady of the Green Kirtle, Miraz, Coriakin, and of course Reepicheep (he was in last year's too though). Anyway, we were all together for Thanksgiving, and she was asking me about who some of these guys were. Now she wants to watch PC and VDT (though I'd strongly prefer she read the books, for obvious reasons
). But I think most people enjoy LWW but leave it at that. There are 6 other books, and it was great to share the awesomeness that is Narnia!