This is an interesting project; Gillian James has attempted to illustrate the non-Dark Tower connections in the Stephen King fictional universe. Leaving out the Dark Tower stuff is kind of a big deal - most of King's fiction eventually weaves its way through the story of Roland the Gunslinger and his ka-tet - but it would be a pretty major-league enormous chart with it left in.
James has done a good effort, but she's left a lot out. And I see an error or two - for instance I'm not sure about the listed connection between Carrie and The Dead Zone, as I believe those two prom fires were totally unrelated events. So here's the challenge: come into the comments and help fill in the blanks (ie, Bill Denbrough gets name dropped in Bag of Bones) and see if we can't put together a better chart.