What is the process to get a new
s.tk shortened URL added to the list?
Since we're currently in testing for using S.TK, we're not rolling it out across the entire network as a general purpose shortener. That means that there are no S.tk links automatically created (such as through the sharing tools) and instead, the need to all be created manually.
Right now, we're keeping it to general resources and the homepages for all of the SE sites. You can see a pretty good list of all the S.TK links here
If you have a suggestion for another resource that you think deserves it's own S.TK link, you can request it at http://s.tk/linkrequest