So, I came across an article on NPR (fangirl squee!) on comic geeks, separating them into grazers (those who read through their comics in whatever order they appear in their box in) and stackers (those who arrange their comics in a particular order to read).
Now, western manga and anime geekdom has expanded during the age of the Internet-- doubtless in some part because of the Internet. As such, we don't have any such ritual as the weekly trip to a comic shop to pick up our volumes. Au contraire; some of us buy online, some of us buy at book stores, some of us do in fact buy at comic shops, and some of us-- ahem –don't buy at all (tsk tsk!).
Nonetheless, this lack of a common purchasing method and location doesn't mean we don't have our own splits. Here are a few that I've noticed-- and keep in mind that these are generalizations, so there are naturally exceptions!
Anime Fans and Manga Fans – In my experience, most anime fans also read manga, or at least are open to reading a manga here and there. By contrast, I have definitely come upon plenty of manga fans who don't watch anime very much, if at all. It's also been my observation that people who are fans of just manga are more likely to also be fans of a much wider range of comics (i.e. they're more likely to be fans of western comics as well). It also seems to me that manga fans are less likely to be into cosplaying, fanfiction, and some of the other common community activities.
Social Otaku and Non-Social Otaku – Note that I say non-social, not anti-social, though of course there are some of those in the otaku world too. But for some people, watching anime (or even reading manga) is a social experience: you do it at anime club or with friends at home, you do it so you can join discussions online; for these people it is as much about the community as it is about the content itself. Other otaku like what they like without having much interest in what others think. They may participate in online forums, but usually more because they're driven to create fanart or fanfiction, or even photograph and document conventions, than because they're interested in socializing.
Casual Fan and “True” Otaku – I'm including this one because I think it's important that we, as the hardcore fans who spend all this time talking about anime and manga in the 'net, the ones who attend conventions, cosplay, write fanfiction, whatever, acknowledge that there are fans whose views are rarely represented on sites such as these. These are the fans who drum up numbers for Naruto and Bleach but don't participate in online forums, don't delve out into more series that are less mainstream. It's an interesting phenomenon, to watch the industry attempt to cater to both of these groups with certain titles, to varying degrees of success.
These are just a few distinctions I've come upon throughout the years-- have you noticed any? Also, of these, I'm an anime-social-otaku.