The Rabbit Web forum has been around, in some form or another, longer than almost any other rabbit website, and at one time it was considered by many as one of the top 2 or 3 rabbit websites in existence. Its present incarnation is here, though it has died down in recent years. The people there are still very knowledgeable though, and are very good about answering questions and such.
Another forum that I like, though I don't visit it very often, is the Rabbit Habbit forum. It seems to be a lot more active than the Rabbit Web forum. The main thing I *don't* like about it is that many of the posters there have enormous signatures, which are distracting from the actual content. But that's a relatively minor complaint.
Rabbit Habbit is a great place I've been a member since 2006. Netherland Dwarf Network is another good place. Bunny Talk is another good one. So is Rabbit Addicts. I have a list of about 20, if you PM me I can get you the links.