Steemit.Chat is a platform allows you to chat with other steemians and was one of the first options back then. There are tons of channels there and a lot of topics to talk about. Many of the channel's subjects are general and many are very specific.
When you'll join for the first time, you'll see two channels, General and Post Promotion. The first one is just for chatting while the latter is for promoting your own post which can get you a few more upvotes.
On the left column, you'll find a button says "More Channels" which will give you a list of channels to find your desired topic.
