Here's what I am really digging so far...
I've not read a bunch of Stephen King. Hardly any really, but I've read IT which happens to take place in the same town as Insomnia.
There are all these little tid-bit mentions of things that pertain to IT (which preceeded Insomnia), particularly around the sewer and storm drains, the rebuilding thereof, a certain memorable rainstorm, etc.
What makes this so cool for me is that it adds this whole other dimension of creepy for the reader. Ralph, our protagonist, was not in any way associated with previous happenings...and therefore me, the reader, knows more about what is possible in Derry than he does. Every time these little tid-bits are mentioned it's like King is saying, "Remember, remember Dear Reader, evil lurks..."
Which is pretty awesome.