D'oh, in my original list of yuri fangirls in anime and manga, I listed the obvious examples, but I forgot two more very fun characters.
Many, many thanks to Akiko Morishima-sensei for creating Hanjuku Joshi. Update on 03/20/2009: I'm not including a pic of Chie because there aren't any available, and I don't want to post any scanlated manga pages here. A chapter title page is okay, if nothing else is available.
5. Chie from Hanjuku Joshi by Akiko Morishima (manga): She seems to be more of a yaoi fangirl, but her starry-eyed meta-fictional lecture about the character dynamics in yuri to her little sister Chitose (who is one of the two protagonists of a girl's school yuri manga lol) makes her a fun addition to an already enjoyable story.
A plethora of thanks to Milk Morinaga-sensei for creating Girl Friends. Tamamin's the one on the right.
6. Tamamin from Girl Friends by Milk Morinaga: A hardcore otaku friend of the two protagonists, Mari and Akko, who deserves this spot for giving Milk Morinaga an excuse to create a meta-fictional parody series titled Revolutionary Pretty Girl Marriage (which draws influence from what I call the unofficial holy trinity of shoujo yuri- Sailor Moon, Revolutionary Girl Utena, and Maria-sama ga Miteru), further cementing the fact that Mari is definitely gay, while raising a few questions about Tamamin. Her fangirl antics provide effective comic relief in what is otherwise a very drama-heavy series.