Are there any good implementations of spatial indexes in Haskell such as R-tree, kd-tree, etc...
The only implementations I'm aware of are the spacepart package, which seems to be incomplete and abandoned, and the KdTree package, which as you might guess has no ambitions beyond providing a kd-tree type.
This is something that's been on my TODO list for a while, since there have been several occasions where I wanted a spatial index data structure, but didn't want one badly enough to stop everything and write a decent implementation on the spot.