I am impressed by the new functionality in Google Maps API V3: StyledMaps
You can create your own dynamic style for Google Maps tiles - and change the look and feel of the base maps which you want to include in your website.
It is quite a natural step, something what open-source projects like Cascadenik and products of other companies such as CloudMade made possible already some time ago. The adoption of this functionality by Google brings this possibility to masses.
If you want to define your own styles for the map you can use the online Style Map Wizard tool. More info and the official announcement is available here.