Generally, to me, a cross-linking dedicated x-risk-forum, a literature list and perhaps also a wiki seem like useful things which don't already exist.

There are several small organizations which are created by one person and limited to a small website that nobody reads.

Seems like a good idea to write a discussing post gathering the names and links to the websites of such groups (or persons), as well as more well-known groups, aiming to get a comprehensive list. In addition to being useful in itself such a list could provide a starting point for people to contact about your ideas of a forum and a wiki.

1. Open complete library of all literature on existential risks.

Similarly, it seems like a comprehensive bibliography of X-risk literature would be a useful resource. Seth Baum's GCR bibliography might be a good starting point.