Just the more mature communities.
The blockland community isn't exactly mature. I'd say that 90% of the lego pages out there are more mature than us. Most of the good builders that frequent lego galleries (brickshelf, mocpages) alot are adults.
Anyways, we should advertise a little on every single lego forum/gallery there is. We could submit some nice builds to mocpages, maybe create a group if there are enough of us. But we should NOT comment on random threads/pictures and ask them to check out Blockland. That would be considered begging and make us look unprofessional.
I'm gonna post a couple of pictures of my own builds on MocPages once I've gotten my new computer. Hopefully, I'll get some attention.