For the folks out there who are creating Google Maps Mashups, here are a few how-tos from the Gmaps.YellowBkpk wiki:
Add Your Own Custom Map
To really spice things up you may want to add your own map...a map that looks the way you want it to look. This off-API Hack shows you how to add your own custom map.
Automatic Tile Cutter
Google Maps are made of dozens to thousands of tile images, depending on the zoom level. At the distant zoom levels you only need a few images to cover a large area. For example, the [www.onnyturf.com/subwaymap.php NYC Subway Map] uses 49 images to cover the greater metropolitan area at zoom level 5. But at the closer zoom levels, thousands of images are required. It takes more than 3500 images to cover the NYC metropolitan area at zoom level 2.
Creating and then uniquely naming each of these images would be a daunting task if you had to do it by hand. That’s why we use a script to do this. The following will show you how to configure a batch processing script to use with Photoshop 7 or CS that will carve all the tiles you need from one big image into hundreds of smaller GIFs, and name them exactly as you need them named.