Webcams.travel have been given their own layer on Google Earth (which you can read about on the Google Earth Blog). However the Webcams.travel website also makes liberal use of Google Maps.
Each webcam on the site (and they have indexed thousands) is accompanied by its own Google Map showing the location of the webcam.
Here is a handy tip. If you click on the option to 'Enlarge map' the map opens up in its own window. Above the new larger map is a search box. Using this search box you can find all the webcams in a particular town. For example searching for 'Washington' returns a map of Washington with all the webcams for the capital tagged on the map.
Some other webcam maps:
Fisgonia - This English/Spanish webcams map has over 300 camera views from all over the world in 11 categories.
300 Great Lakes webcams (US & Canada)
LiveLook - Webcam map with a night / day guide.
USA Webcam Map