The place to be for every hybridizer or if you're planning on taking up hosta sowing.
One of the best forums on the web. It's loaded with information, pictures and useful tips. You'll find enthusiasts here from all over the world.
Extremely useful and unique is the existence of a HVX-forum: everyone with a hart for hostas should pay this section every now and again.
I think this is the largest hosta forum around. It's really fascinating to blend in with the crowd, and with a bit of digging, there are always new things you can learn. But it seems to become a victim of its own success: due to the enormous amount of messages, older topics tend to disappear quite rapidly. The oldest messages are about six months old. I think it's a pity, because massive amounts of useful information are lost in oblivion like this.
My favorite forum, since it is the only Dutch speaking forum with a decent number of active members. It's hasn't been around for too long yet (2006) but Jeroen Linneman, the moderator, gave us hosta geeks from Belgium and the Netherlands our own meeting point.