Well, I run an okay-sized Lord of the Rings site. It's been up about 5 months and we recently broke the 1,000 user mark. Not huge, but good activity and really good dedication among the user base.
We've recently added a whole slew of features including the new Image Gallery, as well as several hacks from this very site which users are playing around with and generally loving.
I had to modify a tonne of the hacks (learn PHP, I'm an ASP'er) so it was a good day of learning yesterday

Thanx to everyone so far for their help and you never know, I may one day release my own first hack
Site: http://www.ringquest.com