It is not dead, but also not progressing very fast. I think low adoption rate is their biggest hurdle, and subsequent lack of network effects in the development community. Solid based on a bunch of Linked Data standards which find most traction in small academic circles. Few sexy applications or good libraries to build from.

The Gitter channels are apparently most active.

Web: https://solidproject.org/

Forum: https://forum.solidproject.org/

Gitter channels, etc: https://github.com/solid/information/blob/master/gitter-chat...

Repo: https://github.com/solid/solid

It's not dead! It's just no longer at MIT (as is also mentioned on the website you linked). Tim founded a startup called inrupt (disclosure: I work there, opinions my own) that aims to stimulate commercial adoption. The links in the sibling comment by rapnie are an excellent place to start.