Not much at the moment, but from what I can tell its a moderated site (in terms of copyrighted stuff) where users can post files they shared on the network, and others can download them on the Sia network (downloads are paid with Siacoin). Basically a search engine that’s currently available on the Web but should work on Tor as well. Maybe also as a decentralized app for those with full Sia nodes.
https://siafiles.com/#/browse/
They (Sia) also work with some company that has Dapps that can be deployed on Sia (also not much at the moment, and too complicated for my liking) but it can’t be denied they are making progress.