You can host pretty much anything you can imagine (short of the obvious, such as illegal content). The Droplet you deploy is a blank slate, so you’d be able to install pretty much any web server, programming language, database server or package that you need and once setup, you could then install pretty much any script (such as a social networking script).
The only thing to keep in mind is that DigitalOcean is not shared hosting, so setting up the server would be something you would need to do on your own (of course, there are multiple tutorials to help guide you through this!). This means you would be responsible for installing the web server (Apache, NGINX, Caddy etc), PHP (via mod_php, PHP-FPM etc), MySQL (or MariaDB/Percona) etc. None of these things are pre-installed for you.