The Google Maps API lets you style maps too [1]. You can change colors and show/hide different map features. There's also a wizard [2] to make styling easier. You can get some very interesting effects [3].

[1] http://googlegeodevelopers.blogspot.com/2010/05/add-touch-of...

[2] http://gmaps-samples-v3.googlecode.com/svn/trunk/styledmaps/...

[3] http://googlegeodevelopers.blogspot.com/2010/10/five-great-s...