No, there is no mailing list.
For discussions and help requests, this forum is the main contact point. The GitHub tracker gives an overview of the planned, confirmed features and bugfixes.
If you want to help, you could have a look at open issues on GitHub, there are also some that don't need deep SFML knowledge (although not many
). Otherwise we really appreciate user input in the forum, so don't hesitate to participate in public discussions.