The magazine, Sky and Telescope in the July, 1995 issue did a comparison of the many 'light pollution' sky filters that were commercially available. Generally, these filters can be effective in increasing the contrast between the sky and a particular class of object you want to study. They are only effective, however, for nebulae and galaxies. You will not magically see more stars with these filters. The best method is still to get to a rural 'dark' site away from city lights. The kind of lighting your town has decided to use also makes a difference to the effectiveness of these filters. Low pressure sodium lights have a few bright spectral lines, and filters can block out much of this 'narrow-band' light. High pressure sodium lights, however, emit in a continuum and require 'broad band' filters which diminish both the light from the street lights, and the light from most kinds of nebulae.