Centroidal Voronoi methods you mean? i.e. approximating a continous space with discrete points (generators) and for the sake of modeling evaluate the neighborhood around each generator as having the same value?
Example. Here is a guy who encodes images with unicode in twitter. He is quantizing in both the spacial and color spaces.
http://www.flickr.com/photos/quasimondo/3518306770/in/photostream/
Here is a paper I wrote about it in 2001. You can use them to cluster the behavior of time series data. Useful for both portfolio diversification and so you can make fine models for each cluster of time series data.
http://orion.math.iastate.edu:80/reu/2001/voronoi_paper/voronoi.pdf