Check out Community Announce a new community where you can announce your new community or find out who is creating new communities.
The more people who use Community Announce to announce new communities and to follow the creating of communities the more effective it becomes.
To fully use communities, you need to be using the beta site. This will allow you to create, join, browse, and participate in communities. If you want to learn more about communities, I created a tutorial video about communities that covers a lot of the common questions.
This community is only for announcing communities so users have an easy way to know what new communities are being formed. You can use the beta site to create a post or just use #hive-122359 tag as your first tag and it will assign your post to this community. You can only post to a single community in your post, even when using the tag method.
Keep in mind, if you create a post in a community you will need to resteem your own post if you want it to be visible outside of communities. If you feel the main audience of Steem would be interested in your post this is a good idea, but it is also good to keep related community posts inside of the community only. There is no standard rule when to do this and it is a judgement call.