One very good example of convergence/fan culture is the Harry Potter series. I have read all seven of the books by J.K. Rowling multiple times and I've seen all the movies. There is a huge fan culture associated with the series, and I wouldn't call myself a huge fan so I haven't experienced all of it. Just like the romance novel fans in the article by Janice Radway, there are things fans do and do not like about the movie series. The books are golden, so fans get in an uproar whenever the movies change the plot a little and stray away from the books. For example, I was pretty upset with the last fight scene between Harry and Voldemort in the last movie because it was nothing at all like what happened in the book. Apart from the movies and books, there are a lot of other things associated with the series in the fan culture that I take part in. For example, my friends and I always go to the movies together when they come out (we dressed up as movie characters for the last one), we have Harry Potter marathon nights, take online quizzes to see which "house" we would be in, among other things. My personal favorite is the fan-made production "A Very Potter Musical" and the sequel, which are both on YouTube. Also, the U has a Quidditch team that I was in last year, so I guess I am a HP nerd.
I don't take part in all fan culture things, however. For example, there is a lot of Harry-Potter themed "fan fiction" out there that continues Harry's story after Rowling's books. There is also tons of Harry Potter merchandise like t-shirts, wands, brooms, etc. There is even the "World of Harry Potter" theme park in Orlando, Florida that I've never been to but I would love to visit someday! Now that the books are over, some fans just can't let go. For these people, Rowling wrote a companion book based on a scene in The Deathly Hallows called The Tales of Beedle the Bard (I've read it), and made some kind of HP experience website called Pottermore (I have not read it).
Listing all these things makes me think that Harry Potter has arguably one of the biggest and most dedicated fan cultures in America. Also, I didn't realize before just how much of this fan culture I take part in, so I guess I'm more of a Harry Potter nerd than I thought.