Sci-Hub does a great job linking DOI with the associated paper. I am looking for a data set that links DOI with other materials pertaining to the paper such as source code, slide or poster.
This is an on going area of exploration and prototypes both in commercial publishing and semi-academic projects. Crossref, DataCite, and Figshare all provide a technical metadata and infrastructure to enable this but there is, as of yet, no (or weak) consensus on how to achieve this end. So, look what these company's are doing. Also, look for "overlay journals" in your field as these provide the kind of links you are looking for.