Basic Idea: Add A book marking tool of some sort to the fan-fic forums.
Basicly you can book mark a certain area of the post and comeback to where that bookmark is by clicking a bookmark finder button or something like that in the fan-fic forums
Why I think this is usefull: I love to read fan-fics and some of the longer ones or ones that have a large amount of chapters some times its easy to lose where you are in the fic/chapter of the fic when you are off line or doing something besides reading it online and you come back on to read some more. This would make it easyer to find where you where and get back to reading.
Limits: I think you could only have 1 or 2 book marks at a time per user.