I think forums only work above a certain level of traffic, email groups are much better for low levels.
The problem being that if you check every day for a week, and there is nothing to interest you, you may never browse there again:
with push technology (such as email) if there is important info to be sent out 2 months since the last post, subscribers will STILL receive it.
Because of this critical mass I don't think there is room for more than a handful of (UK based) cycling sites. My club has its own and it ONLY JUST struggles along with a few posts a week. I am sure most members never visit, despite using a web-browser every day. I nearly suggested we start our own sub-forum in The Old Place - in hindsight that was a narrow escape!
Does any forum software have a usable email notification feature that would deal with this in-betweeny traffic level?