As people here have mentioned, you can tie most of King's work into the Dark Tower, and that is kind of the thematic point of the series. But really, you don't need to. I have read all of King's seventies and eighties works and very little of what came afterward but I still knew enough to "get" the references in the series.
The only thing you need to read in order is the Dark Tower series itself. Nothing in the series gives away major plot points of the other novels and it would probably be just as cool to read The Stand or Salem's Lot after finishing DT. Those of us who grew up in the seventies and eighties had to wait years for the series to finish but I think it would be a lot of fun to read all seven (or eight) books in order.